Switch NDK libraries to 4.9 for x86_64 and mips64

Android NDK r10b doesn't even provide 4.8 for those
archs.

Change-Id: I10840c6c7bbc0dd9028a794162d021d8b3e6b19a
(cherry picked from commit fabd383bc876ff803a3565ccedd9b61559bf5127)
diff --git a/core/combo/TARGET_linux-x86_64.mk b/core/combo/TARGET_linux-x86_64.mk
index 89e42f9..2adb157 100644
--- a/core/combo/TARGET_linux-x86_64.mk
+++ b/core/combo/TARGET_linux-x86_64.mk
@@ -23,7 +23,7 @@
 endif
 
 # Decouple NDK library selection with platform compiler version
-TARGET_NDK_GCC_VERSION := 4.8
+TARGET_NDK_GCC_VERSION := 4.9
 
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
 TARGET_GCC_VERSION := 4.8