Fixup for r172828: use InternalScopedBuffer in favor of large stack buffers

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@172975 91177308-0d34-0410-b5e6-96231b3b80d8
Temporary disable test added in r172828 as it seems to be flaky on the buildbots

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@172976 91177308-0d34-0410-b5e6-96231b3b80d8
CMake: Add add_compiler_rt_static_runtime function and use it to build generic compiler-rt libraries

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@172977 91177308-0d34-0410-b5e6-96231b3b80d8