Upgrade x86 gcc to 4.9 and disable devirtualization.

Also filter out gcc-only flags -Wno-clobbered and -fno-devirtualize
when compiled with clang/llvm.

BUG: 19872411
Change-Id: I6de57583be04da607f569df65e93531787dbb789
diff --git a/core/combo/TARGET_linux-x86.mk b/core/combo/TARGET_linux-x86.mk
index ed78372..958885c 100644
--- a/core/combo/TARGET_linux-x86.mk
+++ b/core/combo/TARGET_linux-x86.mk
@@ -23,10 +23,10 @@
 endif
 
 # Decouple NDK library selection with platform compiler version
-$(combo_2nd_arch_prefix)TARGET_NDK_GCC_VERSION := 4.8
+$(combo_2nd_arch_prefix)TARGET_NDK_GCC_VERSION := 4.9
 
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
-$(combo_2nd_arch_prefix)TARGET_GCC_VERSION := 4.8
+$(combo_2nd_arch_prefix)TARGET_GCC_VERSION := 4.9
 else
 $(combo_2nd_arch_prefix)TARGET_GCC_VERSION := $(TARGET_GCC_VERSION_EXP)
 endif
@@ -97,6 +97,10 @@
 			-include $(android_config_h) \
 			-I $(dir $(android_config_h))
 
+# Work around gcc 4.9 devirtualization bug, https://b.corp.google.com/19872411.
+$(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS += \
+			-fno-devirtualize \
+
 $(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS += $(arch_variant_cflags)
 
 ifeq ($(ARCH_X86_HAVE_SSSE3),true)   # yes, really SSSE3, not SSE3!