perl: Disable setlocale usage under musl

While setlocale() is present, musl currently doesn't provide a suitable implementation.
It'll silently accept every locale, even if not present at all, defaulting them
to C.UTF-8. This will confuse applications as well as our testsuite(see lib/locale.t).

Even if a locale does exist, it's effects will not apply to an extent that will
satisfy many applications.

Avoid further mischief here and just disable setlocale() for now.

Signed-off-by: Marcel Denia <naoir@gmx.net>

lang/perl/files/libc.config

 }
 
 ($owrt:libc eq 'musl') {
+	# musl does not provide a working setlocale(). It accepts arbitrary locales
+	# and makes them act as if they were C.UTF-8.
+	d_setlocale='undef'
+	
 	d_stdio_ptr_lval='undef'
 	d_stdio_ptr_lval_sets_cnt='undef'
 	d_stdiobase='undef'