Improve handling of GCC_DEP variable in Makefile

[embray]

This is a followup to #25188 that I thought was worth doing while fixing that issue. However, since it's not strictly needed for the fix I'll make it a separate ticket.

Depends on #25188

CC: @vbraun

Component: build

Author: Erik Bray

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/25198

[embray]

Dependencies: #25188

[sagetrac-git]

Changed commit from 14b6f4d to b33c210

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. Last 10 new commits:

2965003	add vim modeline for this file
f5f68da	Add a package that by all rights should be included in this list
15c7b88	move this list into a TOOLCHAIN_DEPS variable we can use to inspect this list elsewhere
1954e5e	Add -k/--keep-existing to sage-spkg
f1411c5	From -clean targets in the Makefile, just remove the package's
9976091	Use sage-spkg --keep-existing when installing/re-installing packages in
22a1f34	Revert to using sage-spkg-uninstall in -clean targets, but add a
d71c88f	Merge branch 'u/embray/ticket-25857' into u/embray/build/ticket-25188
f062068	fix accidentally removed blank line needed to make debugging output look better
b33c210	Reduce some unnecessary text duplication in the Makefile.

[embray]

comment:4

I believe this issue can reasonably be addressed for Sage 8.4.

[dimpase]

comment:5

Toolchain packages are unconditionally built - it's also not addressed on #24919.
Anyhow this ought to be dealt with a follow-up to #24919.

[dimpase]

Reviewer: Dima Pasechnik

[kiwifb]

comment:7

Needs rebasing.

[dimpase]

Changed commit from b33c210 to 7647e1f

[dimpase]

comment:8

(automatically) rebased.

[dimpase]

Changed branch from u/embray/build/ticket-25188-2 to public/build/ticket-25188-2

[kiwifb]

comment:9

I was lead here because Volker selected this ticket for inclusion in his merging branch and when I looked on github to see the content of the commit, it came empty. vbraun@0c158ca

Then clicking here resulted in a failure to merge. So Volker will need to re-merge this one now.

Ping @vbraun the content of this ticket is currently missing in the merge.

[embray]

Changed commit from 7647e1f to none

[embray]

Changed branch from public/build/ticket-25188-2 to none

[embray]

comment:10

(Edited, because I was mistaken slightly about the relation of this ticket to #24919.)

This doesn't seem right. This branch just looks identical to the one on #25857 now.
However, this branch should not actually be merged anyways.

These changes are already included implicitly in #24919 which is positively reviewed and should be merged.

The reason this is confusing is that I worked on this ticket at the same time as #24919, but #24919 redid a lot of configure stuff so it included those changes by necessity.

If we just merge #24919, this ticket can be closed as fixed.

[embray]

comment:11

I take it back. Apparently I'm wrong. #24919 does not incorporate all elements of this ticket. Apparently at some point I decoupled them somewhat.

I'll create a new branch...

[embray]

comment:12

Okay, apparently I ended up rolling this back into #25188, hence the empty merge.