From the build directory, run:

  cmake -DCMAKE_TOOLCHAIN_FILE=../build/android.toolchain.cmake ..

Everything compiles and links. unittests, vk-unittests and ReactorUnitTests are known to work.
A "rundroid.sh" script is provided to upload and run Android binaries.
This CL has contains the first draft of an NDK-based FrameBuffer implementation.
It stubs out the gralloc calls in Image (consequence: EGLImage likely won't work).

NOTE: a small CMake patch is necessary; hopefully we'll find a way around this or land it in
CMake:

diff cmake-3.10/Modules/Platform/Android/Determine-Compiler-NDK.cmake.bak cmake-3.10/Modules/Platform/Android/Determine-Compiler-NDK.cmake
231c231
<   set(_ANDROID_TOOL_C_COMPILER_EXTERNAL_TOOLCHAIN ${CMAKE_ANDROID_NDK}/toolchains/${_ANDROID_TOOL_NAME}/prebuilt/${_ANDROID_HOST_DIR})
---
>   set(_ANDROID_TOOL_C_COMPILER_EXTERNAL_TOOLCHAIN ${CMAKE_ANDROID_NDK}/toolchains/${_ANDROID_TOOL_LLVM_NAME}/prebuilt/${_ANDROID_HOST_DIR})

Bug: b/129942368
Change-Id: I107a2f719256b6477ad105054ca68c676c05ec5c
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27869
Presubmit-Ready: Stephen White <senorblanco@chromium.org>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Stephen White <senorblanco@chromium.org>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>