Fix compilation of CodeLayout.cpp for MacOS

llvm/lib/Transforms/Utils/CodeLayout.cpp uses std::abs() with double argument,
which is provided by cmath header, which is not explicitly included into CodeLayout.cpp.
The implicit include in llvm/include/llvm/Support/MathExtras.h was removed in
commit 16544cbe

Inserting explicit include of cmath into CodeLayout.cpp in order to fix build on MacOS.

Committed on behalf of alsemenov (Aleksei Semenov)
Reviewed By: thieta
Differential Revision: https://reviews.llvm.org/D135072