Add TARGET_GCC_VERSION

Default to 4.6, but can overwritten to something else in
prebuilts/gcc/$os/$arch/$arch-linux-android*-$ver

Change-Id: I16f99d642b8ff8e831d392261a0c536041107051
diff --git a/core/combo/TARGET_linux-mips.mk b/core/combo/TARGET_linux-mips.mk
index 1e649ec..8aa6495 100644
--- a/core/combo/TARGET_linux-mips.mk
+++ b/core/combo/TARGET_linux-mips.mk
@@ -43,7 +43,7 @@
 
 # You can set TARGET_TOOLS_PREFIX to get gcc from somewhere else
 ifeq ($(strip $(TARGET_TOOLS_PREFIX)),)
-TARGET_TOOLCHAIN_ROOT := prebuilts/gcc/$(HOST_PREBUILT_TAG)/mips/mipsel-linux-android-4.6
+TARGET_TOOLCHAIN_ROOT := prebuilts/gcc/$(HOST_PREBUILT_TAG)/mips/mipsel-linux-android-$(TARGET_GCC_VERSION)
 TARGET_TOOLS_PREFIX := $(TARGET_TOOLCHAIN_ROOT)/bin/mipsel-linux-android-
 endif
 
@@ -93,10 +93,10 @@
 			-include $(android_config_h) \
 			-I $(arch_include_dir)
 
-# This warning causes dalvik not to build with gcc 4.6.x and -Werror.
+# This warning causes dalvik not to build with gcc 4.6+ and -Werror.
 # We cannot turn it off blindly since the option is not available
 # in gcc-4.4.x.
-ifneq ($(filter 4.6 4.6.%, $(shell $(TARGET_CC) --version)),)
+ifneq ($(filter 4.6 4.6.% 4.7 4.7.%, $(shell $(TARGET_CC) --version)),)
 TARGET_GLOBAL_CFLAGS += -Wno-unused-but-set-variable \
                         -fno-strict-volatile-bitfields
 endif