implement this same as maybe_boot_clouseau

[rnewson]

refinement of #4957 to match maybe_boot_clouseau.

[rnewson]

I'm also questioning whether 4957 did anything as I already had a check for this at the top of boot_nouveau:

def boot_nouveau(ctx):
    if not ctx["with_nouveau"]:
        return

testing locally ./dev/lib/nouveau.yaml is not created when doing dev/run unless you also add --with-nouveau

[jiahuili430]

If nouveau.yaml does not exist in the rel directory, then generate_nouveau_config(ctx) will get FileNotFoundError.
So, I added an if statement to check whether the `nouveau' was enabled.

[rnewson]

I think your testing was based on the PR during its development. The merged version had the

if not ctx["with_nouveau"]:
        return

check in it. As such I think the work in #4957 didn't do anything for the merged version of this work?

Anyway, it makes sense to match the clouseau approach anyway.

[nickva]

+1

[nickva]

Hmm, it would be nice to default to --with-nouveau if we already configured nouveau. I'll see if we can read the install.mk and pick up the dev/run defaults from there perhaps?

[rnewson]

enh, just you ./configure'd with --enable-nouveau doesn't mean you always want to launch it with dev/run, but I guess as a default it makes sense. I'm just used to setting both each time that it doesn't bother me. see how we handle haproxy also

[nickva]

I tried it here #4961, but needed also a way to explicitly disable nouveau during some tests which didn't expect it (mango, etc), so it would need an extra --without-nouveau argument, and that was getting a bit too clunky.