Enable building the native code generator for PowerPC/Mac OS X by default.
It's still not used by default, so you have to specify -fasm when you want
it.
# (as well as a C backend)
#
# Target platforms supported:
-# i386 & sparc
-ifneq "$(findstring $(HostArch_CPP), i386 sparc)" ""
+# i386, sparc & powerpc
+ifneq "$(findstring $(HostArch_CPP), i386 sparc powerpc)" ""
GhcWithNativeCodeGen=YES
else
GhcWithNativeCodeGen=NO