kbuild: add option for stripping modules while installing them

Add option for stripping modules while installing them.

This function adds support for stripping modules while they are being
installed.  CONFIG_DEBUG_KERNEL (which will probably become more
popular as developers use kdump) causes the size of the installed
modules to grow by a factor of 9 or so.

Some kernel package systems solve this problem by stripping the debug
information from /lib/modules after running "make modules_install",
but that may not work for people who are installing directly into
/lib/modules --- root partitions that were sized to handle 16 megs
worth of modules may not be quite so happy with 145 megs of modules,
so the "make modules_install" never succeeds.

This patch allows such users to request modules_install to strip the
modules as they are installed.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/Makefile.modinst b/scripts/Makefile.modinst
index 2686dd5..f0ff248 100644
--- a/scripts/Makefile.modinst
+++ b/scripts/Makefile.modinst
@@ -17,7 +17,7 @@
 	@:
 
 quiet_cmd_modules_install = INSTALL $@
-      cmd_modules_install = mkdir -p $(2); cp $@ $(2)
+      cmd_modules_install = mkdir -p $(2); cp $@ $(2) ; $(mod_strip_cmd) $(2)/$(notdir $@)
 
 # Modules built outside the kernel source tree go into extra by default
 INSTALL_MOD_DIR ?= extra