diff --git a/core/config.mk b/core/config.mk
index e615159..597b0d7 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -444,6 +444,42 @@
 endif
 endif
 
+#
+# Tools that are prebuilts for TARGET_BUILD_APPS
+#
+
+ACP := $(HOST_OUT_EXECUTABLES)/acp
+AIDL := $(HOST_OUT_EXECUTABLES)/aidl
+AAPT := $(HOST_OUT_EXECUTABLES)/aapt
+ZIPALIGN := $(HOST_OUT_EXECUTABLES)/zipalign
+SIGNAPK_JAR := $(HOST_OUT_JAVA_LIBRARIES)/signapk$(COMMON_JAVA_PACKAGE_SUFFIX)
+LLVM_RS_CC := $(HOST_OUT_EXECUTABLES)/llvm-rs-cc
+BCC_COMPAT := $(HOST_OUT_EXECUTABLES)/bcc_compat
+
+DX := $(HOST_OUT_EXECUTABLES)/dx
+MAINDEXCLASSES := $(HOST_OUT_EXECUTABLES)/mainDexClasses
+
+# Override the definitions above for unbundled and PDK builds
+ifneq (,$(TARGET_BUILD_APPS)$(filter true,$(TARGET_BUILD_PDK)))
+prebuilt_sdk_tools := prebuilts/sdk/tools
+prebuilt_sdk_tools_bin := $(prebuilt_sdk_tools)/$(HOST_OS)/bin
+
+ACP := $(prebuilt_sdk_tools_bin)/acp
+AIDL := $(prebuilt_sdk_tools_bin)/aidl
+AAPT := $(prebuilt_sdk_tools_bin)/aapt
+ZIPALIGN := $(prebuilt_sdk_tools_bin)/zipalign
+SIGNAPK_JAR := $(prebuilt_sdk_tools)/lib/signapk$(COMMON_JAVA_PACKAGE_SUFFIX)
+
+DX := $(prebuilt_sdk_tools)/dx
+MAINDEXCLASSES := $(prebuilt_sdk_tools)/mainDexClasses
+
+# Don't use prebuilts in PDK
+ifneq ($(TARGET_BUILD_PDK),true)
+LLVM_RS_CC := $(prebuilt_sdk_tools_bin)/llvm-rs-cc
+BCC_COMPAT := $(prebuilt_sdk_tools_bin)/bcc_compat
+endif # TARGET_BUILD_PDK
+endif # TARGET_BUILD_APPS || TARGET_BUILD_PDK
+
 
 # ---------------------------------------------------------------
 # Generic tools.
@@ -463,8 +499,6 @@
 YASM := prebuilts/misc/$(BUILD_OS)-$(HOST_PREBUILT_ARCH)/yasm/yasm
 
 DOXYGEN:= doxygen
-AAPT := $(HOST_OUT_EXECUTABLES)/aapt$(HOST_EXECUTABLE_SUFFIX)
-AIDL := $(HOST_OUT_EXECUTABLES)/aidl$(HOST_EXECUTABLE_SUFFIX)
 AIDL_CPP := $(HOST_OUT_EXECUTABLES)/aidl-cpp$(HOST_EXECUTABLE_SUFFIX)
 ifeq ($(HOST_OS),linux)
 BREAKPAD_DUMP_SYMS := $(HOST_OUT_EXECUTABLES)/dump_syms
@@ -474,7 +508,6 @@
 endif
 PROTOC := $(HOST_OUT_EXECUTABLES)/aprotoc$(HOST_EXECUTABLE_SUFFIX)
 DBUS_GENERATOR := $(HOST_OUT_EXECUTABLES)/dbus-binding-generator
-SIGNAPK_JAR := $(HOST_OUT_JAVA_LIBRARIES)/signapk$(COMMON_JAVA_PACKAGE_SUFFIX)
 MKBOOTFS := $(HOST_OUT_EXECUTABLES)/mkbootfs$(HOST_EXECUTABLE_SUFFIX)
 MINIGZIP := $(HOST_OUT_EXECUTABLES)/minigzip$(HOST_EXECUTABLE_SUFFIX)
 ifeq (,$(strip $(BOARD_CUSTOM_MKBOOTIMG)))
@@ -519,8 +552,6 @@
 JILL := java -Xmx3500m -jar $(JILL_JAR)
 PROGUARD := external/proguard/bin/proguard.sh
 JAVATAGS := build/tools/java-event-log-tags.py
-LLVM_RS_CC := $(HOST_OUT_EXECUTABLES)/llvm-rs-cc$(HOST_EXECUTABLE_SUFFIX)
-BCC_COMPAT := $(HOST_OUT_EXECUTABLES)/bcc_compat$(HOST_EXECUTABLE_SUFFIX)
 RMTYPEDEFS := $(HOST_OUT_EXECUTABLES)/rmtypedefs
 APPEND2SIMG := $(HOST_OUT_EXECUTABLES)/append2simg
 VERITY_SIGNER := $(HOST_OUT_EXECUTABLES)/verity_signer
@@ -530,12 +561,6 @@
 VBOOT_SIGNER := prebuilts/misc/scripts/vboot_signer/vboot_signer.sh
 FEC := $(HOST_OUT_EXECUTABLES)/fec
 
-# ACP is always for the build OS, not for the host OS
-ACP := $(BUILD_OUT_EXECUTABLES)/acp$(BUILD_EXECUTABLE_SUFFIX)
-
-# dx is java behind a shell script; no .exe necessary.
-DX := $(HOST_OUT_EXECUTABLES)/dx
-ZIPALIGN := $(HOST_OUT_EXECUTABLES)/zipalign$(HOST_EXECUTABLE_SUFFIX)
 ifndef TARGET_BUILD_APPS
 ZIPTIME := $(HOST_OUT_EXECUTABLES)/ziptime$(HOST_EXECUTABLE_SUFFIX)
 endif
diff --git a/tools/ijar/Android.mk b/tools/ijar/Android.mk
index 36f000c..8b2a02c 100644
--- a/tools/ijar/Android.mk
+++ b/tools/ijar/Android.mk
@@ -8,7 +8,7 @@
 include $(CLEAR_VARS)
 LOCAL_CPP_EXTENSION := .cc
 LOCAL_SRC_FILES := classfile.cc ijar.cc zip.cc
-LOCAL_CFLAGS += -Wall
+LOCAL_CFLAGS += -Wall -Werror
 LOCAL_SHARED_LIBRARIES := libz-host
 LOCAL_MODULE := ijar
 # libc++ is not supported for TARGET_BUILD_APPS builds
diff --git a/tools/ijar/classfile.cc b/tools/ijar/classfile.cc
index 5d12cc2..e0cf42e 100644
--- a/tools/ijar/classfile.cc
+++ b/tools/ijar/classfile.cc
@@ -483,12 +483,12 @@
     // We keep an entry if the constant referring to the inner class is already
     // kept. Then we mark its outer class and its class name as kept, too, then
     // iterate until a fixed point is reached.
-    int entry_count;
+    size_t entry_count;
     int iteration = 0;
 
     do {
       entry_count = kept_entries.size();
-      for (int i_entry = 0; i_entry < entries_.size(); ++i_entry) {
+      for (size_t i_entry = 0; i_entry < entries_.size(); ++i_entry) {
         Entry* entry = entries_[i_entry];
         if (entry->inner_class_info->Kept() ||
             used_class_names.find(entry->inner_class_info->Display())
@@ -632,7 +632,7 @@
   }
 
   virtual void ExtractClassNames() {
-    for (int i = 0; i < values_.size(); i++) {
+    for (size_t i = 0; i < values_.size(); i++) {
       values_[i]->ExtractClassNames();
     }
   }
@@ -800,8 +800,8 @@
   };
 
   struct EmptyInfo : TargetInfo {
-    void Write(u1 *&p) {}
-    static EmptyInfo *Read(const u1 *&p) {
+    void Write(u1 *&) {}
+    static EmptyInfo *Read(const u1 *&) {
       return new EmptyInfo;
     }
   };
@@ -1007,7 +1007,7 @@
 // compiler to generate warning messages.
 struct DeprecatedAttribute : Attribute {
 
-  static DeprecatedAttribute* Read(const u1 *&p, Constant *attribute_name) {
+  static DeprecatedAttribute* Read(const u1 *&, Constant *attribute_name) {
     DeprecatedAttribute *attr = new DeprecatedAttribute;
     attr->attribute_name_ = attribute_name;
     return attr;
@@ -1041,7 +1041,7 @@
   }
 
   virtual void ExtractClassNames() {
-    for (int i = 0; i < annotations_.size(); i++) {
+    for (size_t i = 0; i < annotations_.size(); i++) {
       annotations_[i]->ExtractClassNames();
     }
   }
@@ -1112,7 +1112,7 @@
 // and RuntimeInvisibleTypeAnnotations.
 struct TypeAnnotationsAttribute : Attribute {
   static TypeAnnotationsAttribute* Read(const u1 *&p, Constant *attribute_name,
-                                        u4 attribute_length) {
+                                        u4) {
     auto attr = new TypeAnnotationsAttribute;
     attr->attribute_name_ = attribute_name;
     u2 num_annotations = get_u2be(p);
@@ -1124,7 +1124,7 @@
   }
 
   virtual void ExtractClassNames() {
-    for (int i = 0; i < type_annotations_.size(); i++) {
+    for (size_t i = 0; i < type_annotations_.size(); i++) {
       type_annotations_[i]->ExtractClassNames();
     }
   }
@@ -1181,7 +1181,7 @@
   }
 
   void ExtractClassNames() {
-    for (int i = 0; i < attributes.size(); i++) {
+    for (size_t i = 0; i < attributes.size(); i++) {
       attributes[i]->ExtractClassNames();
     }
   }
@@ -1739,7 +1739,7 @@
   members.insert(members.end(), fields.begin(), fields.end());
   members.insert(members.end(), methods.begin(), methods.end());
   ExtractClassNames();
-  for (int i = 0; i < members.size(); i++) {
+  for (size_t i = 0; i < members.size(); i++) {
     Member *member = members[i];
     size_t idx = 0;
     devtools_ijar::ExtractClassNames(member->descriptor->Display(), &idx);
diff --git a/tools/releasetools/edify_generator.py b/tools/releasetools/edify_generator.py
index b3785ac..d923cc8 100644
--- a/tools/releasetools/edify_generator.py
+++ b/tools/releasetools/edify_generator.py
@@ -284,8 +284,8 @@
     cmd = ['apply_patch("%s",\0"%s",\0%s,\0%d'
            % (srcfile, tgtfile, tgtsha1, tgtsize)]
     for i in range(0, len(patchpairs), 2):
-      cmd.append(',\0%s, package_extract_file("%s")' % patchpairs[i:i+2])
-    cmd.append(');')
+      cmd.append(',\0%s,\0package_extract_file("%s")' % patchpairs[i:i+2])
+    cmd.append(') ||\n    abort("Failed to apply patch to %s");' % (srcfile,))
     cmd = "".join(cmd)
     self.script.append(self.WordWrap(cmd))
 
diff --git a/tools/releasetools/ota_from_target_files.py b/tools/releasetools/ota_from_target_files.py
index 1b279e5..5259ede 100755
--- a/tools/releasetools/ota_from_target_files.py
+++ b/tools/releasetools/ota_from_target_files.py
@@ -1572,13 +1572,13 @@
   if OPTIONS.verify and system_diff:
     script.Print("Remounting and verifying system partition files...")
     script.Unmount("/system")
-    script.Mount("/system")
+    script.Mount("/system", recovery_mount_options)
     system_diff.EmitExplicitTargetVerification(script)
 
   if OPTIONS.verify and vendor_diff:
     script.Print("Remounting and verifying vendor partition files...")
     script.Unmount("/vendor")
-    script.Mount("/vendor")
+    script.Mount("/vendor", recovery_mount_options)
     vendor_diff.EmitExplicitTargetVerification(script)
   script.AddToZip(target_zip, output_zip, input_path=OPTIONS.updater_binary)