[IFS][NFC] llvm-ifs: Fixing build errors for bots using GCC.

gcc produces the error:

error: specialization of
‘template<class T, class Enable> struct llvm::yaml::ScalarTraits’ in
different namespace

For all specializations outside of llvm::yaml. So I added llvm::yaml to these
specializations to fix the errors on the bots building with gcc (/usr/bin/c++).

llvm-svn: 370510