kbuild: move archive command to scripts/Makefile.lib

scripts/Makefile.build and arch/s390/boot/Makefile use the same
command (thin archiving with symbol table creation).

Avoid the code duplication, and move it to scripts/Makefile.lib.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index c0abd9a..8a1f64f 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -233,6 +233,12 @@
 quiet_cmd_ld = LD      $@
       cmd_ld = $(LD) $(ld_flags) $(real-prereqs) -o $@
 
+# Archive
+# ---------------------------------------------------------------------------
+
+quiet_cmd_ar = AR      $@
+      cmd_ar = rm -f $@; $(AR) rcsTP$(KBUILD_ARFLAGS) $@ $(real-prereqs)
+
 # Objcopy
 # ---------------------------------------------------------------------------