Fix remaining CI test failures on Linux

This involves a bit of fiddling so we can cross-compile the standard
library tests to musl while on a GNU host. This in turn is necessary as
GitHub's runner doesn't support Alpine on ARM64 hosts for some reason
(actions/runner#801).

.github/workflows/tests.yml

@@ -110,18 +110,20 @@ jobs:
     runs-on: ${{ matrix.target.runner }}
     container:
       image: ghcr.io/inko-lang/ci:fedora
+    env:
+      # This is needed because when setting an explicit target, "ring" looks for
+      # `aarch64-linux-musl-gcc` instead of using `musl-gcc`.
+      CC_aarch64_unknown_linux_musl: musl-gcc
     steps:
       - uses: actions/checkout@v4
       - uses: actions/cache@v4
         with:
           path: '${{ env.CARGO_HOME }}'
           key: ${{ matrix.target.name }}-${{ hashFiles('Cargo.lock', 'rust-toolchain.toml') }}
-      - name: Build the runtime
-        run: cargo build -p rt --target=${{ matrix.target.triple }}
-      - name: Build the compiler
-        run: INKO_RT="${PWD}/target/${{ matrix.target.triple }}/debug" cargo build -p inko
-      - name: Run the tests
-        run: 'cd std && ../target/${{ matrix.target.triple }}/debug/inko test --opt=${{ matrix.level }} --target=${{ matrix.name }}'
+      - name: Build the runtime and compiler
+        run: ./ci/linux.sh ${{ matrix.target.name }} ${{ matrix.target.triple }}
+      - name: Run tests
+        run: 'cd std && ../target/debug/inko test --opt=${{ matrix.level }} --target=${{ matrix.target.name }}'
 
   compiler-mac:
     strategy:

ci/linux.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+
+set -e
+
+INKO_VERSION="$(cargo pkgid -p inko | cut -d\# -f2 | cut -d: -f2)"
+INKO_TRIPLE="${1}"
+RUST_TRIPLE="${2}"
+INKO_RUNTIMES="${HOME}/.local/share/inko/runtimes/${INKO_VERSION}/${INKO_TRIPLE}"
+
+function rustup_lib {
+    local home
+    local toolchain
+    home="$(rustup show home)"
+    toolchain="$(rustup show active-toolchain | awk '{print $1}')"
+
+    echo "${home}/toolchains/${toolchain}/lib/rustlib/${1}/lib/"
+}
+
+# As the host is a GNU host, a bit of extra work is needed to get
+# cross-compilation to musl to work.
+if [[ "${INKO_TRIPLE}" == *-musl ]]
+then
+    cargo build -p rt --target="${RUST_TRIPLE}"
+    mkdir -p "${INKO_RUNTIMES}"
+    cp "./target/${RUST_TRIPLE}/debug/libinko.a" "${INKO_RUNTIMES}/libinko.a"
+    cp "$(rustup_lib "${RUST_TRIPLE}")/self-contained/libunwind.a" \
+        "${INKO_RUNTIMES}/libunwind.a"
+
+    INKO_RT="${PWD}/target/${RUST_TRIPLE}/debug" cargo build -p inko
+else
+    cargo build
+fi