Android: drop static linking of R600 LLVM libraries

Android: drop static linking of R600 LLVM libraries

Inspired by Chih-Wei Huang and Zhen Wu similar patches

Linking against llvm with both static and shared may be avoided,
provided that libLLVM shared library for device supports
whole static R600/AMDGPU libraries, necessary for radeonsi/amdgpu.

Complementary changes, limited to android external/llvm project
are necessary to correclty build libLLVM

Tested with marshmallow-x86 and nougat-x86 builds

Reviewed-by: Chih-Wei Huang <cwhuang@linux.org.tw>
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>