Support tool-specific standard flags in makefile

[jpf91]

This introduces the following new makefile variables: CFLAGS for C, CXXFLAGS for C++, ASFLAGS for Assembler and LDFLAGS for the linker. Names follow conventions from https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html

These variables can then be set either in the user application makefile (before including common.mk) or on the command line when calling make.

Fixes #856

[stnolting]

This looks great! Thanks for implementing this!

You really are one of the few who also note the version number in their PRs. 👍 Anyway, I do not think we need to set a new "version" here. This is just a minor change that is seems to be fully backwards compatible.

It would also be nice if perhaps two lines could be added to the makefile's documentation 😅.

[jpf91]

This looks great! Thanks for implementing this!

Thanks :-)

Anyway, I do not think we need to set a new "version" here.

👍 I was a bit confused as all changelog entries have a new version. I guess I shouldn't add a changelog entry then? Or is it ok to have an entry but keep the old version?

It would also be nice if perhaps two lines could be added to the makefile's documentation 😅.

Good point, I totally forgot about that 😇 I've pushed a new revision which adds the documentation and removes the version change 😄

[stnolting]

I guess I shouldn't add a changelog entry then? Or is it ok to have an entry but keep the old version?

Well, that's a good point... The changelog describes the "version increments" as follows: "The identifier is incremented for each core hardware change and also for major software and/or general project changes."

But this doesn't really clarify how a "major change" is actually defined... 😅

In this case, it is only a minor change that is also fully backwards compatible. I therefore think that it is okay not to assign a new version number for this. 😉

[jpf91]

Thanks!