ppc64 build (using CC="gcc -arch ppc64" CPPFLAGS="-arch ppc64") fails:

  CC     gboxed.lo
../../glib-2.28.8/gobject/gboxed.c: In function 'g_closure_get_type':
../../glib-2.28.8/gobject/gboxed.c:120: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:120: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:120: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:120: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_value_get_type':
../../glib-2.28.8/gobject/gboxed.c:121: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:121: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:121: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:121: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_value_array_get_type':
../../glib-2.28.8/gobject/gboxed.c:122: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:122: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:122: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:122: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_date_get_type':
../../glib-2.28.8/gobject/gboxed.c:123: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:123: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:123: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:123: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_gstring_get_type':
../../glib-2.28.8/gobject/gboxed.c:125: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:125: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:125: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:125: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_hash_table_get_type':
../../glib-2.28.8/gobject/gboxed.c:126: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:126: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:126: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:126: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_array_get_type':
../../glib-2.28.8/gobject/gboxed.c:127: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:127: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:127: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:127: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_ptr_array_get_type':
../../glib-2.28.8/gobject/gboxed.c:128: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:128: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:128: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:128: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_byte_array_get_type':
../../glib-2.28.8/gobject/gboxed.c:129: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:129: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:129: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:129: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_regex_get_type':
../../glib-2.28.8/gobject/gboxed.c:132: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:132: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:132: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:132: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_variant_type_get_gtype':
../../glib-2.28.8/gobject/gboxed.c:138: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:138: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:138: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:138: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_error_get_type':
../../glib-2.28.8/gobject/gboxed.c:141: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:141: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:141: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:141: error: incompatible type for argument 3 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c: In function 'g_date_time_get_type':
../../glib-2.28.8/gobject/gboxed.c:143: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:143: warning: union cannot be made transparent
../../glib-2.28.8/gobject/gboxed.c:143: error: incompatible type for argument 2 of '_g_register_boxed'
../../glib-2.28.8/gobject/gboxed.c:143: error: incompatible type for argument 3 of '_g_register_boxed'
make[4]: *** [gboxed.lo] Error 1
make[3]: *** [all-recursive] Error 1
make[2]: *** [all] Error 2
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2

$ gcc --version
powerpc-apple-darwin9-gcc-4.0.1 (GCC) 4.0.1 (Apple Inc. build 5493)
Copyright (C) 2005 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Same for CC="gcc-4.2 -arch ppc64".

$ gcc-4.2 --version
powerpc-apple-darwin9-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5577)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.