The new toolchain file requires Android NDK r12b and above. Default to use 'arm-linux-androideabi-clang' toolchain and LLVM libc++ STL runtime.
Align all the compiler and linker flags according to new ndk-build configuration in Android NDK r12b, i.e. no more '-f[no-]strict-aliasing' and '-f[no-]omit-frame-pointer', but more stringent warnings check.
Improve over the old toolchain file where most of the options are now changeable after the initial configuration. The exceptions are ANDROID_NDK and ANDROID_TOOLCHAIN_NAME due to limitation of CMake.
Close#1441.
Other changes in this commit includes:
- Fix Android sample launcher app to support shared C++ STL runtime library.
- Remove temporary fix in FindUrho3D module as it is not required anymore with our new toolchain file.
- Fix Log::WriteRaw() method to pass the parameters correctly to __android_log_print() function.
- Fix enable_pch() macro to emit -fPIC compiler flags correctly based on target's POSITION_INDEPENDENT_CODE property.
- Fix linker flags for ld.bfd where it needs help to find the location of the rooted shared libraries. The flags are not required for ld.gold but they do no harm for gold linker.
- Enhance the CheckCompilerToolchain module to auto-detect if the NEON SIMD is enabled or not for Android build (based on the chosen ANDROID_ABI).
When in try_compile() mode, quickly obtain the previously cached values stored in the (inner scope) environment variables and bypass all the checks (which are already done when the toolchain file is being processed at the start of CMake run).
Due to the CMake try_compile() limitation, initial build option values (i.e. not env-vars) were not visible to all the CMake checks during inital configuration, preventing the build option from functioning as expected.
