clang-cl: Remove -O0 option

cl.exe doesn't understand it; there's /Od instead. See also the review
thread for r229575.

Update lots of compiler-rt tests to use -Od instead of -O0.
Ran `rg -l 'clang_cl.*O0' compiler-rt/test/ | xargs sed -i -c 's/-O0/-Od/'`

Differential Revision: https://reviews.llvm.org/D64506

llvm-svn: 365724