Makefile: building git in cygwin 1.7.0

On platforms with $X, make removes any leftover scripts 'a' from
earlier builds if a new binary 'a.exe' is now built.  However, on
cygwin 1.7.0, 'git' and 'git.exe' now consistently name the same file.
Test for file equality before attempting a remove, in order to avoid
nuking just-built binaries.

Signed-off-by: Eric Blake <ebb9@byu.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -1064,7 +1064,7 @@ SHELL = $(SHELL_PATH)
 
 all:: shell_compatibility_test $(ALL_PROGRAMS) $(BUILT_INS) $(OTHER_PROGRAMS) GIT-BUILD-OPTIONS
 ifneq (,$X)
-	$(foreach p,$(patsubst %$X,%,$(filter %$X,$(ALL_PROGRAMS) $(BUILT_INS) git$X)), $(RM) '$p';)
+	$(foreach p,$(patsubst %$X,%,$(filter %$X,$(ALL_PROGRAMS) $(BUILT_INS) git$X)), test '$p' -ef '$p$X' || $(RM) '$p';)
 endif
 
 all::