Verify Nuklear.h is clean before running tests

[RobLoach]

Fixes #890

[RobLoach]

@sleeptightAnsiC line 1: syntax error near unexpected token `then'

Looks pretty gross lol. Likely a cleaner way to do that.

[sleeptightAnsiC]

Sorry, I have no idea how to reliably test this on my local machine, and just doing it blindly. According to this SO thread, the | should enable multilines, so it should be fine now (I hope!)

Suggested change

	run: make nuke && \
	if ! git diff --exit-code nuklear.h ; then \
	echo "Did you forgot to rebuild ./nuklear.h ?" >/dev/stderr ; \
	echo "Make sure to apply your changes to ./src/* first, and only then rebuild the amalgamation with ./src/paq* !" >/dev/stderr ; \
	exit 1 ; \
	fi ;
	run: |
	make nuke
	if ! git diff --exit-code nuklear.h ; then
	echo "Did you forgot to rebuild ./nuklear.h ?" >/dev/stderr
	echo "Make sure to apply your changes to ./src/* first, and only then rebuild the amalgamation with ./src/paq* !" >/dev/stderr
	exit 1
	fi

[sleeptightAnsiC]

I have no idea how to reliably test this on my local machine

Found this one: https://github.com/nektos/act
I'm installing it right now.

[RobLoach]

Moved it to a Makefile command, and avoided the nesting.

[sleeptightAnsiC]

It does work!

[sleeptightAnsiC]

@RobLoach ah sh1t, I was 5sec too late. Mind reverting your last commit (c2a909b) and accepting this one (#907 (comment)) instead?

No need to have a partial step in the Makefile. It wouldn't really work without CI and could confuse us in the future. Better keep everything in the workflow file alone.

[sleeptightAnsiC]

this can be resolved

[sleeptightAnsiC]

Just for the record, I had a very different idea on how to implement this. Wanted something that will be possible to run outside of CI. Got some prototype at: https://gist.github.com/sleeptightAnsiC/900062bb7bc0c47b5395e496b452500d

Rob decided this would be too complex. In case only CI is involved, I tend to agree.