kbuild: change kbuild to not rely on incorrect GNU make behavior

The kbuild system takes advantage of an incorrect behavior in GNU make.
Once this behavior is fixed, all files in the kernel rebuild every time,
even if nothing has changed.  This patch ensures kbuild works with both
the incorrect and correct behaviors of GNU make.

For more details on the incorrect behavior, see:

http://lists.gnu.org/archive/html/bug-make/2006-03/msg00003.html

Changes in this patch:
  - Keep all targets that are to be marked .PHONY in a variable, PHONY.
  - Add .PHONY: $(PHONY) to mark them properly.
  - Remove any $(PHONY) files from the $? list when determining whether
    targets are up-to-date or not.

Signed-off-by: Paul Smith <psmith@gnu.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/sh/Makefile b/arch/sh/Makefile
index 08c9515c4806..c72e17a96eed 100644
--- a/arch/sh/Makefile
+++ b/arch/sh/Makefile
@@ -172,7 +172,7 @@ include/asm-sh/.mach: $(wildcard include/config/sh/*.h) include/config/MARKER
 
 archprepare: maketools include/asm-sh/.cpu include/asm-sh/.mach
 
-.PHONY: maketools FORCE
+PHONY += maketools FORCE
 maketools:  include/linux/version.h FORCE
         $(Q)$(MAKE) $(build)=arch/sh/tools include/asm-sh/machtypes.h