Disable canonical prefixes of system headers

GCC know a few pre-defined paths (relative to its location) to
search for headers, libraries, program, etc.  By default GCC prefixes
its own path(argv[0]) and calls realpath() which result in absolute
path with all symlink, . and .. removed.

It's usually good to have canonicalised paths, but absolute paths
in *.d file can cause unnecessary relinking when stale entries
in ccache cache hit

Add -no-canonical-prefixes (gcc>=4.6) and
-fno-canonical-system-headers (gcc>4.6) to disable realpath() on
prefixed paths

Change-Id: I58d739e61fb013015fb05a9c98b2132b307f915a

core/clang/config.mk

@@ -31,7 +31,8 @@ CLANG_CONFIG_UNKNOWN_CFLAGS := \
   -funswitch-loops \
   -Wno-psabi \
   -Wno-unused-but-set-variable \
-  -Wno-unused-but-set-parameter
+  -Wno-unused-but-set-parameter \
+  -fno-canonical-system-headers
 
 # Clang flags for all host rules
 CLANG_CONFIG_HOST_EXTRA_ASFLAGS :=

core/combo/HOST_linux-x86.mk

@@ -52,7 +52,8 @@ HOST_GLOBAL_LDFLAGS += -static
 endif # BUILD_HOST_static
 
 HOST_GLOBAL_CFLAGS += -fPIC \
-    -include $(call select-android-config-h,linux-x86)
+  -no-canonical-prefixes \
+  -include $(call select-android-config-h,linux-x86)
 
 # Disable new longjmp in glibc 2.11 and later. See bug 2967937.
 HOST_GLOBAL_CFLAGS += -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0

core/combo/TARGET_linux-arm.mk

@@ -103,6 +103,8 @@ $(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS += \
 			-Werror=format-security \
 			-D_FORTIFY_SOURCE=2 \
 			-fno-short-enums \
+			-no-canonical-prefixes \
+			-fno-canonical-system-headers \
 			$(arch_variant_cflags) \
 			-include $(android_config_h) \
 			-I $(dir $(android_config_h))

core/combo/TARGET_linux-arm64.mk

@@ -87,6 +87,8 @@ TARGET_GLOBAL_CFLAGS += \
 			-Werror=format-security \
 			-D_FORTIFY_SOURCE=2 \
 			-fno-short-enums \
+			-no-canonical-prefixes \
+			-fno-canonical-system-headers \
 			$(arch_variant_cflags) \
 			-include $(android_config_h) \
 			-I $(dir $(android_config_h))

core/combo/TARGET_linux-mips.mk

@@ -90,6 +90,8 @@ $(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS += \
 			-Wa,--noexecstack \
 			-Werror=format-security \
 			-D_FORTIFY_SOURCE=2 \
+			-no-canonical-prefixes \
+			-fno-canonical-system-headers \
 			$(arch_variant_cflags) \
 			-include $(android_config_h) \
 			-I $(dir $(android_config_h))

core/combo/TARGET_linux-mips64.mk

@@ -95,6 +95,8 @@ TARGET_GLOBAL_CFLAGS += \
 			-Wa,--noexecstack \
 			-Werror=format-security \
 			-D_FORTIFY_SOURCE=2 \
+			-no-canonical-prefixes \
+			-fno-canonical-system-headers \
 			$(arch_variant_cflags) \
 			-include $(android_config_h) \
 			-I $(dir $(android_config_h))

core/combo/TARGET_linux-x86.mk

@@ -122,6 +122,8 @@ $(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS += \
 			-fstack-protector \
 			-m32 \
 			-msse2 \
+			-no-canonical-prefixes \
+			-fno-canonical-system-headers \
 			-include $(android_config_h) \
 			-I $(dir $(android_config_h))
 

core/combo/TARGET_linux-x86_64.mk

@@ -120,7 +120,9 @@ TARGET_GLOBAL_CFLAGS += \
 			-funswitch-loops \
 			-funwind-tables \
 			-fstack-protector \
-			-m64
+			-m64 \
+			-no-canonical-prefixes \
+			-fno-canonical-system-headers
 
 # Help catch common 32/64-bit errors.
 TARGET_GLOBAL_CFLAGS += \