Make Clang host builds hermetic on Linux.

This lays the groundwork for making builds hermetic on Darwin as well.
That will be fixed in a future patch.

bug 13435344

Change-Id: Iae82d0b9efad0598d682ff5fd4daa737aa607866
diff --git a/core/combo/HOST_darwin-x86.mk b/core/combo/HOST_darwin-x86.mk
index 037dee6..994196a 100644
--- a/core/combo/HOST_darwin-x86.mk
+++ b/core/combo/HOST_darwin-x86.mk
@@ -156,3 +156,7 @@
 define get-file-size
 stat -f "%z" $(1)
 endef
+
+# gcc location for clang; to be updated when clang is updated
+# HOST_TOOLCHAIN_ROOT is a Darwin-specific define
+HOST_TOOLCHAIN_FOR_CLANG := $(HOST_TOOLCHAIN_ROOT)
\ No newline at end of file
diff --git a/core/combo/HOST_linux-x86.mk b/core/combo/HOST_linux-x86.mk
index 129acb0..3c87264 100644
--- a/core/combo/HOST_linux-x86.mk
+++ b/core/combo/HOST_linux-x86.mk
@@ -41,10 +41,14 @@
 # which can benefit from 64-bit host arch.
 HOST_GLOBAL_CFLAGS += -m64 -Wa,--noexecstack
 HOST_GLOBAL_LDFLAGS += -m64 -Wl,-z,noexecstack
+# gcc location for clang; to be updated when clang is updated
+HOST_TOOLCHAIN_FOR_CLANG := prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.7-4.6/
 else
 # We expect SSE3 floating point math.
 HOST_GLOBAL_CFLAGS += -mstackrealign -msse3 -mfpmath=sse -m32 -Wa,--noexecstack
 HOST_GLOBAL_LDFLAGS += -m32 -Wl,-z,noexecstack
+# gcc location for clang; to be updated when clang is updated
+HOST_TOOLCHAIN_FOR_CLANG := prebuilts/gcc/linux-x86/host/i686-linux-glibc2.7-4.6/
 endif # BUILD_HOST_64bit
 
 ifneq ($(strip $(BUILD_HOST_static)),)