Use -Werror in system/extras

* Remove unused variables.
* Fix redefined macro warnings.
* Fix sign-compare warnings.
* Fix 'return false' in main().
* Keep existing warnings to fix later.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: Ib92ef5297693595fb84ed4f8e61665bda4cee312
diff --git a/ext4_utils/Android.mk b/ext4_utils/Android.mk
index a80e473..6f26dd6 100644
--- a/ext4_utils/Android.mk
+++ b/ext4_utils/Android.mk
@@ -21,6 +21,7 @@
 LOCAL_SHARED_LIBRARIES_linux += libselinux
 LOCAL_CFLAGS_darwin := -DHOST
 LOCAL_CFLAGS_linux := -DHOST
+LOCAL_CFLAGS += -Wall -Werror
 include $(BUILD_HOST_EXECUTABLE)
 
 
@@ -30,6 +31,7 @@
 LOCAL_SHARED_LIBRARIES := libcutils
 LOCAL_CFLAGS_darwin := -DHOST
 LOCAL_CFLAGS_linux := -DHOST
+LOCAL_CFLAGS += -Wall -Werror
 include $(BUILD_HOST_EXECUTABLE)
 
 #
@@ -49,7 +51,7 @@
     libext4_utils \
     libselinux \
     libz
-LOCAL_CFLAGS := -DREAL_UUID
+LOCAL_CFLAGS := -DREAL_UUID -Wall -Werror
 include $(BUILD_EXECUTABLE)
 
 
@@ -57,11 +59,13 @@
 LOCAL_SRC_FILES := setup_fs.c
 LOCAL_MODULE := setup_fs
 LOCAL_SHARED_LIBRARIES += libcutils
+LOCAL_CFLAGS := -Wall -Werror
 include $(BUILD_EXECUTABLE)
 
 
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := ext4fixup_main.c
+LOCAL_CFLAGS := -Wall -Werror
 LOCAL_MODULE := ext4fixup
 LOCAL_SHARED_LIBRARIES += \
     libext4_utils \
@@ -72,6 +76,7 @@
 
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := ext4fixup_main.c
+LOCAL_CFLAGS := -Wall -Werror
 LOCAL_MODULE := ext4fixup
 LOCAL_STATIC_LIBRARIES += \
     libext4_utils \