Arguably "-std=c++11" is redundant during linking, so this one is fine. But "-stdlib=libc++" is required for linking, and adding it to LDFLAGS will definitely not work, example (openmpi) given in my previous comments. Also, handling them in multiple places (CXXFLAGS and LDFLAGS) is adding burden to maintenance and unnecessary as compiler support them both during compiling and linking. I wouldn't consider them CXXFLAGS, but part of the compiler command.