Add support for AArch64 XOM binaries.

Adds build system support for generating AArch64 binaries with
execute-only memory layouts via a new LOCAL_XOM property. Also adds
support for an ENABLE_XOM build flag for global builds.

Bug: 77958880
Test: make -j ENABLE_XOM=true
Change-Id: I6af9e3615d0a9fdff802eae50e6ad94311ec8046
diff --git a/core/binary.mk b/core/binary.mk
index d7112b6..23defdc 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -73,6 +73,30 @@
   my_native_coverage := false
 endif
 
+ifeq ($(strip $(ENABLE_XOM)),true)
+  ifndef LOCAL_IS_HOST_MODULE
+    my_xom := true
+    # Disable XOM in excluded paths.
+    combined_xom_exclude_paths := $(XOM_EXCLUDE_PATHS) \
+                                  $(PRODUCT_XOM_EXCLUDE_PATHS)
+    ifneq ($(strip $(foreach dir,$(subst $(comma),$(space),$(combined_xom_exclude_paths)),\
+           $(filter $(dir)%,$(LOCAL_PATH)))),)
+      my_xom := false
+    endif
+
+    # Allow LOCAL_XOM to override the above
+    ifdef LOCAL_XOM
+      my_xom := $(LOCAL_XOM)
+    endif
+
+    ifeq ($(strip $(my_xom)),true)
+      ifeq (arm64,$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH))
+        my_ldflags += -Wl,-execute-only
+      endif
+    endif
+  endif
+endif
+
 my_allow_undefined_symbols := $(strip $(LOCAL_ALLOW_UNDEFINED_SYMBOLS))
 ifdef SANITIZE_HOST
 ifdef LOCAL_IS_HOST_MODULE