Merged android.toolchain.cmake from project
https://github.com/taka-no-me/android-cmake
commit: fd1f7055f8b7338644d58d9a2015a784dfa3a5ca

Order returned by CMake is unreliable but we need clang to go after gcc for
automatic toolchain selection.

Ticket #2426

It is needed because of explicit STL include paths.
Otherwise some standard headers (like fenv.h) can not not be correctly found by the compiler.

* fix formatting
* honor Windows-style paths
* suppress warnings inside try_compile
* correct caching of toolchain variables

To speed up rebuilds, define the NDK_CCACHE environment or CMake variable
to the path to your ccache binary. When declared, the android.cmake.toolchain
automatically uses CCache when compiling any C/C++ source file. For example:

export NDK_CCACHE=ccache

# Please enter the commit message for your changes. Lines starting
# with '#' will be kept; you may remove them yourself if you want to.
# An empty message aborts the commit.
# On branch master
# Your branch is ahead of 'origin/master' by 1 commit.
#
# Changes to be committed:
#   (use "git reset HEAD^1 <file>..." to unstage)
#
#	modified:   android/android.toolchain.cmake
#