Makefile: POSIX windres

When environment variable POSIXLY_CORRECT is set, the
"input -o output" syntax is not supported.

  http://cygwin.com/ml/cygwin/2017-01/msg00036.html

Use "-i input -o output" syntax instead.

Signed-off-by: Steven Penny <svnpenn@gmail.com>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -1816,7 +1816,7 @@ $(SCRIPT_LIB) : % : %.sh GIT-SCRIPT-DEFINES
 git.res: git.rc GIT-VERSION-FILE
 	$(QUIET_RC)$(RC) \
 	  $(join -DMAJOR= -DMINOR=, $(wordlist 1,2,$(subst -, ,$(subst ., ,$(GIT_VERSION))))) \
-	  -DGIT_VERSION="\\\"$(GIT_VERSION)\\\"" $< -o $@
+	  -DGIT_VERSION="\\\"$(GIT_VERSION)\\\"" -i $< -o $@
 
 # This makes sure we depend on the NO_PERL setting itself.
 $(SCRIPT_PERL_GEN): GIT-BUILD-OPTIONS