ci: Simplify musl build setup

No need to setup symlink farms, we can just use the host's /usr/include
now.

.github/workflows/build-test-musl.sh

@@ -1,24 +0,0 @@
-#!/bin/bash
-# SPDX-License-Identifier: LGPL-2.1-or-later
-
-set -eux
-
-if ! command -v musl-gcc >/dev/null; then
-    echo "musl-gcc is not installed, skipping the test."
-    exit 77
-fi
-
-TMPDIR=$(mktemp -d)
-
-cleanup() (
-    set +e
-
-    if [[ -d "$TMPDIR" ]]; then
-        rm -rf "$TMPDIR"
-    fi
-)
-
-trap cleanup EXIT ERR INT TERM
-
-tools/setup-musl-build.sh "${TMPDIR}/build"
-ninja -v -C "${TMPDIR}/build"

.github/workflows/linter.yml

@@ -81,4 +81,12 @@ jobs:
         run: mkosi box -- meson test -C build --suite=clang-tidy --print-errorlogs --no-stdsplit --quiet
 
       - name: Build with musl
-        run: mkosi box -- .github/workflows/build-test-musl.sh
+        run: |
+          mkosi box -- \
+            env \
+            CC=musl-gcc \
+            CXX=musl-gcc \
+            CFLAGS="-idirafter /usr/include" \
+            CXXFLAGS="-idirafter /usr/include" \
+              meson setup -Dlibc=musl -Ddbus-interfaces-dir=no musl
+          mkosi box -- ninja -C musl