Fix logic issue when using -fvisibility-ms-compat.
Fix logic issue when using -fvisibility-ms-compat.

Only use this flag when building with clang (Apple or upstream
versions) on Mac.

Signed-off-by: 13c070840a6ad1a6bd5ec250484ecbd6f037ec10@mathworks.com

ksubramz/CppMicroServices,CppMicroServices/CppMicroServices,ksubramz/CppMicroServices,CppMicroServices/CppMicroServices,ksubramz/CppMicroServices,CppMicroServices/CppMicroServices,CppMicroServices/CppMicroServices,ksubramz/CppMicroServices,saschazelzer/CppMicroServices,CppMicroServices/CppMicroServices,saschazelzer/CppMicroServices,ksubramz/CppMicroServices