Add scripts/gcc-toolchain.sh

[am11]

With this script present in the official repository, both rust and dotnet can source it from a single source of truth. e.g. https://github.com/am11/arcade/blob/cc67bb38f3bcafe34c3d04b92cb04747b3d58a97/eng/common/cross/build-rootfs.sh#L284

I have made some modifications (additional commits) on @jclulow's original script from his rust fork.

• Cherry-pick initial commit from jclow/rust.
• Parameterize SYSROOT_DIR.
• Rev binutils to 2.33.1.
  • with v2.25.1, we were getting the relocation error from assembler (as) or archiever (ar?):

    ....pal/src/libcoreclrpal.a(context2.S.o): warning: relocation against CONTEXT_CaptureContext' in readonly section .text'.
    ....pal/src/libcoreclrpal.a(context2.S.o): relocation R_X86_64_PC32 against symbol `CONTEXT_CaptureContext' can not be used when making a shared object; recompile with -fPIC
    ....final link failed: Bad value

  • only revving buildutils version fixed the error above and build went through (without any code modifications).
• Overwrite existing links.
  • when we re-run the script, ln -fs (instead of ln -s) avoids removing the existing links.
• Remove xtrace.
  • we can use bash -x scripts/gcc-toolchain.sh.

[am11]

cc @jclulow, please take a look. :)

Aside, I have not yet figured out how to include these few headers in sysroot's Makefile: https://github.com/am11/arcade/blob/cc67bb38f3bcafe34c3d04b92cb04747b3d58a97/eng/common/cross/build-rootfs.sh#L313. If you could help getting those headers in the sysroot's next release, that would be great. Meanwhile, I am fetching them from illumos-gate repo for dotnet libraries build.

[am11]

As per the discussion on IRC, due to the different version requirements in various downstreams, I have inlined this script in: dotnet/arcade#5584.

When next release of sysroot will pick up the missing headers, I will cleanup the wget calls to acquire those headers from illumos-gate repository.