kbuild: create KBUILD_OUTPUT

kbuild: create KBUILD_OUTPUT

When requesting build to another directory, try to create it first.

---

,-*- bash -*-

|olecom@deen:~/kernel.org/_work/src/linux-2.6.20-rc5$
|olecom@deen:~/kernel.org/_work/src/linux-2.6.20-rc5$ make O=/tmp/build
|cd: 1: can't cd to /tmp/build
|Makefile:116: *** output directory "/tmp/build" does not exist.  Stop.
|olecom@deen:~/kernel.org/_work/src/linux-2.6.20-rc5$ patch -p1 <../../va-patch/
|kbuild-create-output-dir.patch
|patching file Makefile
|olecom@deen:~/kernel.org/_work/src/linux-2.6.20-rc5$ make O=/tmp/build
|HOSTCC scripts/basic/fixdep HOSTCC scripts/basic/docproc make[3]: ***
|[scripts/basic/docproc] Interrupt make[2]: *** [scripts_basic] Interrupt
|make: *** [_all] Interrupt
|
|olecom@deen:~/kernel.org/_work/src/linux-2.6.20-rc5$

`-*-

@@ -113,5 +113,5 @@
 # check that the output directory actually exists
 saved-output := $(KBUILD_OUTPUT)
-KBUILD_OUTPUT := $(shell cd $(KBUILD_OUTPUT) && /bin/pwd)
+KBUILD_OUTPUT := $(shell d=$(KBUILD_OUTPUT) ; mkdir -p $$d && cd $$d && pwd)
 $(if $(KBUILD_OUTPUT),, \
      $(error output directory "$(saved-output)" does not exist))