I did read that for cross-compiling from Windows to Linux, you need to supply the rust-lld linker in the Cargo config; but (un?)fortunately my situation does not seem to be that simple.

On Ubuntu, I installed musl and musl-dev. This means that I have aarch64-linux-musl-gcc in my $PATH and should have the required libraries. However, when I try to cargo build --target aarch64-unknown-linux-musl, I see this:

error: failed to run custom build command for `rquickjs-sys v0.6.2`

Caused by:
  process didn't exit successfully: `/opt/surrealdb/target/debug/build/rquickjs-sys-f5cc455b87df8099/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-changed=build.rs
  cargo:rerun-if-env-changed=CARGO_FEATURE_BINDGEN
  cargo:rerun-if-env-changed=CARGO_FEATURE_UPDATE_BINDINGS
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_BYTECODE
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_GC
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_GC_FREE
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_FREE
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_LEAKS
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_MEM
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_OBJECTS
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_ATOMS
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_SHAPES
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_MODULE_RESOLVE
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_PROMISE
  cargo:rerun-if-env-changed=CARGO_FEATURE_DUMP_READ_OBJECT
  Applying patch patches/error_column_number.patch
  can't find file to patch at input line 5
  Perhaps you used the wrong -p or --strip option?
  The text leading up to this was:
  --------------------------
  |diff --git a/Makefile b/Makefile
  |index 0270a6a..1c78547 100644
  |--- a/Makefile
  |+++ b/Makefile
  --------------------------
  No file to patch.  Skipping patch.
  1 out of 1 hunk ignored
  patching file cutils.c
  patching file cutils.h
  patching file quickjs-atom.h
  patching file quickjs-opcode.h
  patching file quickjs.c
  patching file quickjs.h
  patching file tests/test_line_column.js
  Applying patch patches/get_function_proto.patch
  patching file quickjs.c
  Hunk #1 succeeded at 2222 (offset 7 lines).
  patching file quickjs.h
  Applying patch patches/check_stack_overflow.patch
  patching file quickjs.c
  Hunk #1 succeeded at 1622 (offset 32 lines).
  Applying patch patches/infinity_handling.patch
  patching file quickjs.c
  Hunk #1 succeeded at 10391 (offset 105 lines).
  Hunk #2 succeeded at 43407 (offset 317 lines).
  Hunk #3 succeeded at 49735 (offset 317 lines).
  Bindings for target: aarch64-unknown-linux-gnu

  --- stderr
  Ubuntu clang version 18.1.3 (1ubuntu1)
  Target: aarch64-unknown-linux-gnu
  Thread model: posix
  InstalledDir:
  Found candidate GCC installation: /../lib/gcc/aarch64-linux-gnu/11
  Found candidate GCC installation: /../lib/gcc/aarch64-linux-gnu/13
  Selected GCC installation: /../lib/gcc/aarch64-linux-gnu/13
  Candidate multilib: .;@m64
  Selected multilib: .;@m64
  ignoring nonexistent directory "/usr/include/clang/18.1.3/include/"
  ignoring nonexistent directory "/../lib/gcc/aarch64-linux-gnu/13/../../../../aarch64-linux-gnu/include"
  ignoring nonexistent directory "/include"
  #include "..." search starts here:
  #include <...> search starts here:
   /usr/local/include
   /usr/include/aarch64-linux-gnu
   /usr/include
  End of search list.
  /usr/include/stdio.h:34:10: fatal error: 'stddef.h' file not found
  thread 'main' panicked at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/rquickjs-sys-0.6.2/build.rs:351:39:
  Unable to generate bindings: ClangDiagnostic("/usr/include/stdio.h:34:10: fatal error: 'stddef.h' file not found\n")
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...

A few things stand out to me:

• It's using Clang instead of the totally available GCC. Do I need to manually specify cc?

• stddef.h is most definitively included in musl. But, just to make sure, I went to verify:

# dpkg -L musl-dev | grep -i stddef
/usr/include/aarch64-linux-musl/stddef.h

Sure enough. Technically, everything should be present. I made sure the target is also installed:

# rustup target list --installed
aarch64-unknown-linux-gnu
aarch64-unknown-linux-musl

So... what exactly am I missing here?

Thanks and kind regards!