temporarily turn on warnings for NPTL

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

extra/Configs/Config.in

@@ -436,6 +436,8 @@ config UCLIBC_HAS_THREADS_NATIVE
 	bool "Native POSIX Threading (NPTL)"
 	select UCLIBC_HAS_TLS
 	select UCLIBC_HAS_STDIO_FUTEXES
+	# NPTL local:
+	select EXTRA_WARNINGS
 	help
 	  If you want to compile uClibc with NPTL support, then answer Y.