[Toybox] scripts/llvm-buildall.sh?

[Rob Landley]

In https://landley.net/toybox/faq.html#cross there are three build options listed:

1) using your linux distro's host toolchain (probably glibc based)

2) using the Android NDK

3) using the musl+gcc toolchain I supply a scripts/mcm-buildall.sh to build

(Except for #3 I won't post binaries of because GPLv3 is too toxic for me to
mess with without a corporate legal department providing cover, which has
admittedly been a limiting factor.)

Recently I've been poking at adding Qualcomm Hexagon support to the
https://landley.net/toybox/downloads/binaries/mkroot/latest/ target list, and
hexagon only has upstream support in llvm, not in vanilla gcc. (Which is
probably my fault actually; long story, related to
https://landley.net/notes-2012.html#24-02-2012.)

I started down this path because I found out last month that qemu had an llvm
build script checked into its test suite, and I went down a longish rathole to
make that work for me (starting at
https://lists.nongnu.org/archive/html/qemu-devel/2021-07/msg02992.html and
https://landley.net/notes-2021.html#12-07-2021 and eventually coming up with a
working script at https://www.openwall.com/lists/musl/2021/07/25/2).

Then I tried to genericize it to build more llvm targets and the "clang-rt"
package (their libgcc replacement) is, um... extremely brittle.
(https://landley.net/notes-2021.html#28-07-2021)

What I'd LIKE to do is create a scripts/llvm-buildall.sh that builds all the
supported musl+llvm targets the way mcm-buildall.sh does for musl+gcc. And
getting llvm-project itself to do that was pretty straightforward (it builds
them all by default). But clang-rt depends on the target libc headers being
there first (...why?) and then the invocation is... yeah.

I'm currently reading https://llvm.org/docs/HowToCrossCompileBuiltinsOnArm.html
but the OTHER llvm toolchain I've been using is the Android NDK, and THAT
successfully builds clang-rt for multiple architectures already:

  android-ndk-r21d$ find . -name 'libclang_rt.*.so' | wc
       22      22    2375
  android-ndk-r21d$ find . -name 'libclang_rt.*.a' | wc
       68      68    7284

Plus it's building bionic from source, which would be nice to know how to do.

So I looked at:

  https://android.googlesource.com/platform/manifest/+/master-ndk/

And, um... huh. Well, clang-rt is part of llvm-project so...

  https://android.googlesource.com/toolchain/llvm-project/+/refs/heads/master

Last updated in 2019?

Am I looking in the wrong place?

Confused,

Rob