[PATCH] headers_check: use a different default directory

`make headers_check' wants to go and write stuff in /lib/modules, which
requires root, whic is unfortunate.

In fact, there's no _particular_ reason for headers_install to put it there
either -- it can go into a subdirectory of the build tree in both cases.
It's not intended to go directly into /usr/include, which is why we didn't
put it there -- and we certainly don't want people screwing around with
symlinking to it.  It's for distributors to take away and do stuff with, so
leaving it in $(objtree) is fine, even in the headers_install case.

I picked $(objtree)/usr/include but I have no _particular_ preference
for that; it just seemed reasonable.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Makefile

@@ -889,7 +889,7 @@ depend dep:
 
 # ---------------------------------------------------------------------------
 # Kernel headers
-INSTALL_HDR_PATH=$(MODLIB)/abi
+INSTALL_HDR_PATH=$(objtree)/usr
 export INSTALL_HDR_PATH
 
 PHONY += headers_install
@@ -986,7 +986,7 @@ CLEAN_FILES +=	vmlinux System.map \
                 .tmp_kallsyms* .tmp_version .tmp_vmlinux* .tmp_System.map
 
 # Directories & files removed with 'make mrproper'
-MRPROPER_DIRS  += include/config include2
+MRPROPER_DIRS  += include/config include2 usr/include
 MRPROPER_FILES += .config .config.old include/asm .version .old_version \
                   include/linux/autoconf.h include/linux/version.h      \
                   include/linux/utsrelease.h                            \
@@ -1077,7 +1077,7 @@ help:
 	@echo  '  kernelrelease	  - Output the release version string'
 	@echo  '  kernelversion	  - Output the version stored in Makefile'
 	@echo  '  headers_install - Install sanitised kernel headers to INSTALL_HDR_PATH'
-	@echo  '                    (default: /lib/modules/$$VERSION/abi)'
+	@echo  '                    (default: $(INSTALL_HDR_PATH))'
 	@echo  ''
 	@echo  'Static analysers'
 	@echo  '  checkstack      - Generate a list of stack hogs'