Our base-clang poses as gcc-4.2.1, but building with clang on powerpc
"requires" gcc>=4.3, unlike other archs requiring lower versions. Instead,
ignore the gcc version check ifdef hell for all base-clang arches.

Index: src/lj_arch.h
--- src/lj_arch.h.orig
+++ src/lj_arch.h
@@ -299,7 +299,7 @@
 #endif
 
 /* Check for minimum required compiler versions. */
-#if defined(__GNUC__)
+#if defined(__GNUC__) && !defined(__clang__)
 #if LJ_TARGET_X86
 #if (__GNUC__ < 3) || ((__GNUC__ == 3) && __GNUC_MINOR__ < 4)
 #error "Need at least GCC 3.4 or newer"