kbuild: kill EXTRA_ARFLAGS

EXTRA_ARFLAGS have never been used so no need to carry
around on this.
A google search did not reveal any external module
using this either.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 7fd6055..e74a837 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -291,7 +291,7 @@
 #
 ifdef lib-target
 quiet_cmd_link_l_target = AR      $@
-cmd_link_l_target = rm -f $@; $(AR) $(EXTRA_ARFLAGS) rcs $@ $(lib-y)
+cmd_link_l_target = rm -f $@; $(AR) rcs $@ $(lib-y)
 
 $(lib-target): $(lib-y) FORCE
 	$(call if_changed,link_l_target)