Failure in configure-android when specifying --use-ndk-cflags with Android NDK r13 or later

[riza]

Starting r13, Android NDK has set NDK_TOOLCHAIN_VERSION default value to Clang.
This will result the configure-android to fail with this error:

configure-android error: compiler not found, please check environment 
settings (TARGET_ABI, etc)

Furthermore, r13 release notes states that:

GCC is no longer supported. It will not be removed from the NDK just yet, 
but is no longer receiving backports. 
It cannot be removed until after libc++ has become stable enough to be the default, 
as some parts of gnustl are still incompatible with Clang. 
It will likely be removed after that point.

So, modification to configure-android which expects gcc would be needed.

At the moment (on r13), you can force the ndk to use gcc by specifying the NDK_TOOLCHAIN_VERSION to 4.9.

e.g:

NDK_TOOLCHAIN_VERSION=4.9 TARGET_ABI=armeabi-v7a ./configure-android --use-ndk-cflags