Adding SKIP_GIT to speed up compiles.

Makefile

@@ -485,6 +485,7 @@ $(SUBPROJECTS): %: %-allkm
 
 # Let's match everything, we handle all the rule parsing ourselves
 .PHONY: %
+ifndef SKIP_GIT
 %:
 	# Check if we have the CMP tool installed
 	cmp --version >/dev/null 2>&1; if [ $$? -gt 0 ]; then printf "$(MSG_NO_CMP)"; exit 1; fi;
@@ -507,6 +508,22 @@ $(SUBPROJECTS): %: %-allkm
 	if [ -f $(ERROR_FILE) ]; then printf "$(MSG_ERRORS)" & exit 1; fi;
 	$(foreach TEST,$(TESTS),$(RUN_TEST))
 	if [ -f $(ERROR_FILE) ]; then printf "$(MSG_ERRORS)" & exit 1; fi;
+else
+%:
+	# Check if we have the CMP tool installed
+	cmp --version >/dev/null 2>&1; if [ $$? -gt 0 ]; then printf "$(MSG_NO_CMP)"; exit 1; fi;
+	rm -f $(ERROR_FILE) > /dev/null 2>&1
+	$(eval $(call PARSE_RULE,$@))
+	$(eval $(call SET_SILENT_MODE))
+	# Run all the commands in the same shell, notice the + at the first line
+	# it has to be there to allow parallel execution of the submake
+	# This always tries to compile everything, even if error occurs in the middle
+	# But we return the error code at the end, to trigger travis failures
+	$(foreach COMMAND,$(COMMANDS),$(RUN_COMMAND))
+	if [ -f $(ERROR_FILE) ]; then printf "$(MSG_ERRORS)" & exit 1; fi;
+	$(foreach TEST,$(TESTS),$(RUN_TEST))
+	if [ -f $(ERROR_FILE) ]; then printf "$(MSG_ERRORS)" & exit 1; fi;
+endif
 
 # All should compile everything
 .PHONY: all
@@ -526,7 +543,11 @@ test: test-all
 test-clean: test-all-clean
 
 # Generate the version.h file
-GIT_VERSION := $(shell git describe --abbrev=6 --dirty --always --tags 2>/dev/null || date +"%Y-%m-%d-%H:%M:%S")
+ifndef SKIP_GIT
+    GIT_VERSION := $(shell git describe --abbrev=6 --dirty --always --tags 2>/dev/null || date +"%Y-%m-%d-%H:%M:%S")
+else
+    GIT_VERSION := NA
+endif
 BUILD_DATE := $(shell date +"%Y-%m-%d-%H:%M:%S")
 $(shell echo '#define QMK_VERSION "$(GIT_VERSION)"' > $(ROOT_DIR)/quantum/version.h)
 $(shell echo '#define QMK_BUILDDATE "$(BUILD_DATE)"' >> $(ROOT_DIR)/quantum/version.h)