Document some missing options in configure -h

Signed-off-by: Andreas Faerber <andreas.faerber@web.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7023 c046a42c-6fe2-441c-8c8c-71466251a162

configure

diff --git a/configure b/configure
index 412828e..853541d 100755
--- a/configure
+++ b/configure
@@ -554,6 +554,8 @@
 echo "  --cross-prefix=PREFIX    use PREFIX for compile tools [$cross_prefix]"
 echo "  --cc=CC                  use C compiler CC [$cc]"
 echo "  --host-cc=CC             use C compiler CC [$host_cc] for dyngen etc."
+echo "  --extra-cflags=CFLAGS    add C compiler flags CFLAGS"
+echo "  --extra-ldflags=LDFLAGS  add linker flags LDFLAGS"
 echo "  --make=MAKE              use specified make [$make]"
 echo "  --install=INSTALL        use specified install [$install]"
 echo "  --static                 enable static build [$static]"