local ccvers="$( (unset CHOST; gcc --version 2>/dev/null) )"
local mycc=
case "${ccvers}" in
*"Apple LLVM version "*)
*"Apple "*" version "*)
vers=${ccvers#*Apple LLVM version }
vers=${ccvers#*Apple * version }
vers=${vers% (clang-*}
# let's assume that >=llvm-3.6 is able to compile
# libcxx, so select the matching Apple versions, see