build: Convert git_sha1_gen script to Python (part2).

Things pointed out by Emil.

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/Makefile.am

@@ -21,7 +21,7 @@
 
 .PHONY: git_sha1.h.tmp
 git_sha1.h.tmp:
-	@python $(top_srcdir)/bin/git_sha1_gen.py > $@
+	@$(PYTHON2) $(top_srcdir)/bin/git_sha1_gen.py > $@
 
 git_sha1.h: git_sha1.h.tmp
 	@echo "updating git_sha1.h"

src/mesa/Android.libmesa_git_sha1.mk

@@ -46,7 +46,7 @@ LOCAL_GENERATED_SOURCES += $(addprefix $(intermediates)/, git_sha1.h)
 $(intermediates)/git_sha1.h: $(wildcard $(MESA_TOP)/.git/logs/HEAD)
 	@mkdir -p $(dir $@)
 	@echo "GIT-SHA1: $(PRIVATE_MODULE) <= git"
-	$(hide) python $(MESA_TOP)/bin/git_sha1_gen.py > $@
+	$(hide) $(MESA_PYTHON2) $(MESA_TOP)/bin/git_sha1_gen.py > $@
 
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(intermediates)