snappy won't build with gcc because of the always_inline attribute

This patch only allows that attribute when using clang

input from sthen and kn

ok kn sthen

archivers/snappy/patches/patch-snappy-stubs-internal_h

@@ -0,0 +1,14 @@
+Don't set this for gcc, it keeps snappy from building
+
+Index: snappy-stubs-internal.h
+--- snappy-stubs-internal.h.orig
++++ snappy-stubs-internal.h
+@@ -99,7 +99,7 @@
+ #endif
+ 
+ // Inlining hints.
+-#ifdef HAVE_ATTRIBUTE_ALWAYS_INLINE
++#if defined(HAVE_ATTRIBUTE_ALWAYS_INLINE) && defined(__clang__)
+ #define SNAPPY_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
+ #else
+ #define SNAPPY_ATTRIBUTE_ALWAYS_INLINE