rustc-src: enable rustix use-libc feature, revert ported attributes

[LinuxUserGD]

Workarounds for the following bugs:

• rustix: enable use-libc feature

This patches the rustix dependency in all cargo crates to include the use-libc feature.
The workaround for #365 was mentioned in https://www.github.com/thepowersgang/mrustc/issues/365#issuecomment-3904762958.

• Revert attributes ported to new parsing infrastructure

The stage0 rustc fails to compile any project with the error "out of TLS keys" on musl.
This happens because the thread-local storage was bumped with the recent additions/ports of attribute parsers in Rust 1.90.0 (see termux/termux-packages#26682, rust-lang/rust#147590).

--- BUILDING rustc-main v0.0.0 [bin rustc_main] (99.4% 2r,0w,0b,317c/319t)
> /usr/lib/rust/mrustc-9999/bin/mrustc /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/rustc-1.90.0-src/compiler/rustc/src/main.rs -o /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/rustc_main -C emit-depfile=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/rustc_main.d --cfg debug_assertions -O -L /usr/lib/rust/mrustc-9999/lib/rustlib/x86_64-unknown-linux-musl/lib -L /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build --cfg feature="llvm" --cfg feature="rustc_driver_impl" --cfg feature="dep:rustc_driver_impl" --crate-name rustc_main --crate-type bin --crate-tag 0_0_0_H44 --edition 2024 --extern rustc_codegen_ssa=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/librustc_codegen_ssa.rlib --extern rustc_driver=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/librustc_driver.rlib --extern rustc_driver_impl=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/librustc_driver_impl.rlib --extern rustc_public=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/librustc_public-0_1_0_H4.rlib --extern rustc_public_bridge=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/librustc_public_bridge.rlib > /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/rustc_main_dbg.txt
 (99.4% 2r,0w,0b,317c/319t): rustc-main v0.0.0 (script run), rustc-main v0.0.0 [bin rustc_main]
Completed rustc-main v0.0.0 (script run)
 (99.7% 1r,0w,0b,318c/319t): rustc-main v0.0.0 [bin rustc_main]
Completed rustc-main v0.0.0 [bin rustc_main]
 (100.0% 0r,0w,0b,319c/319t):
rustc 1.90.0-stable-mrustc
 * Building 'sysroot' using bootstrap rustc (mrustc-stage0) ...
 * env MRUSTC_PATH=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/rustc minicargo -j 24 --vendor-dir /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/rustc-1.90.0-src/vendor --script-overrides /usr/share/mrustc-9999/script-overrides/stable-1.90.0-linux/ --output-dir /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/lib/rustlib/x86_64-unknown-linux-musl/lib /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/rustc-1.90.0-src/library/sysroot
--- BUILDING core v0.0.0 (0.0% 1r,0w,21b,0c/22t)
> /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/rustc /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/rustc-1.90.0-src/library/core/src/lib.rs -o /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/lib/rustlib/x86_64-unknown-linux-musl/lib/libcore.rlib --emit link,dep-info -C debug-assertions -Z force-unstable-if-unmarked -O -L /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/lib/rustlib/x86_64-unknown-linux-musl/lib --crate-name core --crate-type rlib -C metadata=0_0_0 --edition 2024 > /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/lib/rustlib/x86_64-unknown-linux-musl/lib/libcore.rlib_dbg.txt
 (0.0% 1r,0w,21b,0c/22t): core v0.0.0
warning: due to multiple output types requested, the explicitly specified output file name will be adapted for each output type

fatal runtime error: out of TLS keys, aborting
Process was terminated with signal 6
FAILING COMMAND: /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/rustc-build/rustc /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/rustc-1.90.0-src/library/core/src/lib.rs -o /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/lib/rustlib/x86_64-unknown-linux-musl/lib/libcore.rlib --emit link,dep-info -C debug-assertions -Z force-unstable-if-unmarked -O -L /var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/lib/rustlib/x86_64-unknown-linux-musl/lib --crate-name core --crate-type rlib -C metadata=0_0_0 --edition 2024
Env:  OUT_DIR=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/bootstrap/mrustc-stage0/lib/rustlib/x86_64-unknown-linux-musl/lib/build_core CARGO_CRATE_NAME=core CARGO_MANIFEST_DIR=/var/tmp/portage/dev-lang/rust-1.90.0-r1/work/rustc-1.90.0-src/library/core CARGO_PKG_NAME=core CARGO_PKG_VERSION=0.0.0 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=0 CARGO_PKG_VERSION_PATCH=0
 (4.5% 0r,0w,21b,1c/22t):
BUILD FAILED

Instead of bumping the limit by changing the musl source code, I've reverted the relevant commits (e. g. "Port #[rustc_coherence_is_core] to the new attribute system") from rust's git history.

Fixes #388 (rust 1.90.0 packaging)

[bjorn3]

That revert patch is pretty big and will almost certainly cause huge conflicts in the next release. Would patching away the -Ztls-model=initial-exec in src/bootstrap/src/bin/rustc.rs also fix the issue? That flag is just a minor perf optimization.

[LinuxUserGD]

Would patching away the -Ztls-model=initial-exec in src/bootstrap/src/bin/rustc.rs also fix the issue?

The error also occurs when removing it from bin/rustc.rs.
I also get the same behaviour with the clang flag -ftls-model=initial-exec (or similar) in codegen_c.cpp.

I'm not sure how to solve this issue in mrustc, maybe patching minicargo (https://github.com/thepowersgang/mrustc/blob/master/tools/minicargo/build.cpp) would work.