[ASan tests] Use clang-cl to build tests on Windows

Reviewed at http://reviews.llvm.org/D3680

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@208526 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] define ASAN_DYNAMIC=1 if PIC is defined

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@208530 91177308-0d34-0410-b5e6-96231b3b80d8