Makefiles: Remove abuses of FORCE and .PHONY

[jcarrano]

Description

What

FORCE and .PHONY targets are being abused in RIOT's makefile. For example:

RIOT/Makefile.include

Line 383 in d6b2a9e

$(ELFFILE): FORCE

RIOT/Makefile.include

Line 404 in d6b2a9e

$(BINDIR)/$(APPLICATION_MODULE).a: FORCE

RIOT/Makefile.include

Line 443 in d6b2a9e

.PHONY: pkg-prepare $(USEPKG:%=$(BINDIR)/%.a)

Why

This is incorrect. It triggers unnecessary rebuilds and may hide problems with the makefiles.

How to solve it.

Targets should depend on their prerequisites only. To solve this:

• Replace .PHONY with FORCE where it makes sense. This is a first step on making the code less wrong. (see Makefile.include: Replace PHONY by FORCE #9623)
• If the force is there to work around configuration variable changes, these should be made into a target. (see dist/tools: add lazysponge tool #9634 )
• Remove the FORCE and PHONY.

[cladmi]

I would still say, more important than not rebuilding for nothing, which "only" wastes time, we are currently not rebuilding when necessary #9589 for example which makes the build invalid if you do not do make clean all.

But of course both are somehow linked together.

[jcarrano]

@cladmi Of course they are linked. One can say that building too much is the lesser evil, but we should resist the temptation to work around our "too little built" issues by being overly conservative and forcing things to be build.

[jcarrano]

Recursive use of make only complicates matters, see Recursive Make Considered Harmful.
The rule that runs the recursive make has to be forced, because there's no way for the outer make to know things have not been modified.

[cladmi]

I know ;) #1242 #7670

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you want me to ignore this issue, please mark it with the "State: don't stale" label. Thank you for your contributions.

[cladmi]

This is still valid and is in pre-cleaning steps in #10850

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you want me to ignore this issue, please mark it with the "State: don't stale" label. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you want me to ignore this issue, please mark it with the "State: don't stale" label. Thank you for your contributions.