Windows port work by Ruben Van Boxem

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@142578 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__config b/include/__config
index 35a1663..fe39172 100644
--- a/include/__config
+++ b/include/__config
@@ -88,7 +88,11 @@
 #endif
 
 #ifndef _LIBCPP_INLINE_VISIBILITY
-#define _LIBCPP_INLINE_VISIBILITY __forceinline
+# if _MSC_VER
+#  define _LIBCPP_INLINE_VISIBILITY __forceinline
+# else // MinGW GCC and Clang
+#  define _LIBCPP_INLINE_VISIBILITY __attribute__ ((__always_inline__))
+# endif
 #endif
 
 #ifndef _LIBCPP_EXCEPTION_ABI
@@ -97,7 +101,7 @@
 
 #ifndef _LIBCPP_ALWAYS_INLINE
 # if _MSC_VER
-# define _LIBCPP_ALWAYS_INLINE __forceinline
+#  define _LIBCPP_ALWAYS_INLINE __forceinline
 # endif
 #endif