[PATCH v2] Makefile: Improve compiler header dependency check

[David Aguilar <davvid@gmail.com>]

Make the check use the same flags as the invocation to avoid
false positives when user-configured compiler flags contain
incompatible options.

For example, it is possible to build universal git binaries on
OS X with the following snippet in config.mak:

	CFLAGS = -arch i386 -arch x86_64

111ee18c31f9bac9436426399355facc79238566 breaks this setup and
results in the following error message:

	gcc-4.2: -E, -S, -save-temps and -M options are
	not allowed with multiple -arch flags

Include ALL_CFLAGS so that this and other conditions are caught.
Use SHELL_PATH instead of assuming that "sh" is a sane shell.

Signed-off-by: David Aguilar <davvid@gmail.com>
---
I'm not sure if "sh -c" is necessary but I did notice that other
parts of the Makefile use $(SHELL_PATH).  The check was adjusted
to use that as well.

 Makefile |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index aa67142..9446a4e 100644
--- a/Makefile
+++ b/Makefile
@@ -1250,8 +1250,9 @@ COMPUTE_HEADER_DEPENDENCIES =
 USE_COMPUTED_HEADER_DEPENDENCIES =
 else
 ifndef COMPUTE_HEADER_DEPENDENCIES
-dep_check = $(shell sh -c \
-	'$(CC) -c -MF /dev/null -MMD -MP -x c /dev/null -o /dev/null 2>&1; \
+dep_check = $(shell $(SHELL_PATH) -c \
+	'$(CC) -c -MF /dev/null -MMD -MP -x c /dev/null -o /dev/null \
+	$(ALL_CFLAGS) 2>&1; \
 	echo $$?')
 ifeq ($(dep_check),0)
 COMPUTE_HEADER_DEPENDENCIES=YesPlease
-- 
1.7.7.rc0.308.gc820