bump NDK toolchain to 4.9 (#19945)

Summary:
This PR will bump NDK_TOOLCHAIN_VERSION to 4.9 or use GCC 4.9 to build C++ code. Once merged, we can bump folly to a newer version, which requires GCC 4.9.
Pull Request resolved: #19945

Reviewed By: fkgozali

Differential Revision: D8943282

Pulled By: hramos

fbshipit-source-id: d239ca67a08788b12e115a9d78443b13a10403f6

Author: dulmandakh

ReactAndroid/src/main/java/com/facebook/react/fabric/jsc/jni/BUCK

@@ -7,7 +7,7 @@ rn_xplat_cxx_library(
     compiler_flags = [
         "-Wall",
         "-fexceptions",
-        "-std=gnu++1y",
+        "-std=c++1y",
     ],
     platforms = ANDROID,
     soname = "libfabricjscjni.$(ext)",

ReactAndroid/src/main/jni/Application.mk

@@ -10,6 +10,7 @@ NDK_MODULE_PATH := $(APP_MK_DIR)$(HOST_DIRSEP)$(THIRD_PARTY_NDK_DIR)$(HOST_DIRSE
 APP_STL := gnustl_shared
 
 # Make sure every shared lib includes a .note.gnu.build-id header
+APP_CPPFLAGS := -std=c++1y
 APP_LDFLAGS := -Wl,--build-id
 
-NDK_TOOLCHAIN_VERSION := 4.8
+NDK_TOOLCHAIN_VERSION := 4.9

ReactAndroid/src/main/jni/first-party/fb/Android.mk

@@ -32,7 +32,7 @@ ifeq ($(TOOLCHAIN_PERMISSIVE),true)
 endif
 LOCAL_CFLAGS += -DHAVE_POSIX_CLOCKS
 
-CXX11_FLAGS := -std=gnu++11
+CXX11_FLAGS := -std=c++11
 LOCAL_CFLAGS += $(CXX11_FLAGS)
 
 LOCAL_EXPORT_CPPFLAGS := $(CXX11_FLAGS)

ReactAndroid/src/main/jni/first-party/fbgloginit/Android.mk

@@ -10,7 +10,7 @@ LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)
 LOCAL_CFLAGS := -fexceptions -fno-omit-frame-pointer
 LOCAL_CFLAGS += -Wall -Werror
 
-CXX11_FLAGS := -std=gnu++11
+CXX11_FLAGS := -std=c++11
 LOCAL_CFLAGS += $(CXX11_FLAGS)
 
 LOCAL_EXPORT_CPPFLAGS := $(CXX11_FLAGS)

ReactAndroid/src/main/jni/third-party/boost/Android.mk

@@ -3,7 +3,7 @@ include $(CLEAR_VARS)
 
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/boost_1_63_0
 LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/boost_1_63_0
-CXX11_FLAGS := -std=gnu++11
+CXX11_FLAGS := -std=c++11
 LOCAL_EXPORT_CPPFLAGS := $(CXX11_FLAGS)
 
 LOCAL_MODULE    := boost

ReactAndroid/src/main/jni/third-party/folly/Android.mk

@@ -16,7 +16,7 @@ LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)
 LOCAL_CFLAGS += -fexceptions -fno-omit-frame-pointer -frtti
 LOCAL_CFLAGS += -Wall -Werror -std=c++11
 
-CXX11_FLAGS := -std=gnu++11
+CXX11_FLAGS := -std=c++11
 LOCAL_CFLAGS += $(CXX11_FLAGS)
 
 FOLLY_FLAGS := -DFOLLY_NO_CONFIG=1 -DFOLLY_HAVE_CLOCK_GETTIME=1