Merging r309483:

Merging r309483:
------------------------------------------------------------------------
r309483 | mgorny | 2017-07-29 01:10:24 -0700 (Sat, 29 Jul 2017) | 7 lines

[OCaml] Pass -D/-UNDEBUG through to ocamlc

Detect [/-][DU]NDEBUG in CMAKE_C_FLAGS* and pass them through to ocamlc.
This is necessary because their value might affect visibility of dump
functions in LLVM and ocamlc uses its own compiler and flags by default.

Differential Revision: https://reviews.llvm.org/D35898
------------------------------------------------------------------------

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_50@309591 91177308-0d34-0410-b5e6-96231b3b80d8