dev-lang/rust: attempt to make the build system to honor MAKEOPTS

[stefson]

by default, dev-lang/rust does use one job per thread, which can be a problem if there is not enough memory per job on the build system. It was fixed for src_compile recently in the main tree, however there are some subtle differences in the structure of the ebuilds and I'm not certain if this fix actually works as intended for the musl ebuild provided here.

I will test it, but it might take some time. If someone with more experience thinks the fix will be working, or tests this on his own, I'd be fine with it.

[stefson]

Note to myself - right in the beginning of src_compile there is something wrong

Compiling source in /var/tmp/portage/dev-lang/rust-1.23.0-r1/work/rustc-1.23.0-src ...
running: /var/tmp/portage/dev-lang/rust-1.23.0-r1/work/stage0/bin/cargo build --manifest-path /var/tmp/portage/dev-lang/rust-1.23.0-r1/work/rustc-1.23.0-src/src/bootstrap/Cargo.toml --verbose --verbose --locked --frozen

this command uses all available cores, likeley up to the point where it starts building its internal llvm copy, but this time with the correct value of MAKEOPTS

I can't see anything corresponding in the build, and neither find much informations with search engine when typing 'cargo limit number of jobs' for obvious reasons, but it should be possible to execute

../work/stage0/bin/cargo/build -j$(makeopts_jobs) --manifest-path ../$(PATH)

[stefson]

@lluixhi: I'm failing to fix the number of jobs during early bootstrap, before the internal llvm is build. You got any idea what is going on there? The ebuild itself executes ./x.py during src_compile, that's all. Is it a an upstream bug in the build system?

rust-early-bootstrap.zip
see the build log if it helps

[lluixhi]

Hmmmm I'm not really sure but I'll check it out -- in the meantime I'll merge these.