The steps in the "Build from Source" documentation always fail if the runtime is not cleaned after building with a non-wasi compatible clang

[paulcadman]

To reproduce

Precondition:

• The version of LLVM on your PATH does not support thewasm32-unknown-wasi triple (this is the default on macOS aarch64 even after running brew install llvm as the non-wasi Apple clang at /usr/bin/clang takes precedence)

Steps:

1. Run make in the root of the project. The runtime build will fail with error: unable to create target: 'No available targets are compatible with triple "wasm32-unknown-wasi"'
2. Follow the instructions at https://docs.juvix.org/0.5.4/howto/installing/#building-juvix-from-source
3. Run make CC=$(brew --prefix llvm)/bin/clang LIBTOOL=$(brew --prefix llvm)/bin/llvm-ar build

Expected

The instructions build and installs Juvix from source.

Actual

The build continues to fail at the make runtime stage with the error: error: unable to create target: 'No available targets are compatible with triple "wasm32-unknown-wasi"'

Workaround

After the error in step 1. of the reproduction steps, run (for macOS):

make clean
make CC=$(brew --prefix llvm)/bin/clang LIBTOOL=$(brew --prefix llvm)/bin/llvm-ar build

Explanation

After the initial failing build, the runtime build stores the resolved Makefile parameters as state in the build directory. This state is reused even if the Makefile parameters are subsequently changed.

[paulcadman]

On macOS with recent versions of LLVM (at least 16+) the instructions to install libclang_rt.builtins-wasm32-wasi-*.tar.gz in https://docs.juvix.org/0.5.4/howto/installing/#installing-dependencies are redundant. They may still be necessary on Linux. We should check this and remove this section if possible.