internal/rosa: musl libc artifact

This will likely be included in Rosa OS. The installation is modified to be entirely contained in prefix.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/musl.go

@@ -0,0 +1,67 @@
+package rosa
+
+import (
+	"slices"
+
+	"hakurei.app/internal/pkg"
+)
+
+// MuslAttr holds the attributes that will be applied to musl.
+type MuslAttr struct {
+	// Install headers only.
+	Headers bool
+	// Environment variables concatenated with defaults.
+	Env []string
+	// Dependencies concatenated with defaults.
+	Extra []pkg.Artifact
+}
+
+// NewMusl returns a [pkg.Artifact] containing an installation of musl libc.
+func (t Toolchain) NewMusl(attr *MuslAttr) pkg.Artifact {
+	const (
+		version  = "1.2.5"
+		checksum = "y6USdIeSdHER_Fw2eT2CNjqShEye85oEg2jnOur96D073ukmIpIqDOLmECQroyDb"
+	)
+
+	if attr == nil {
+		attr = new(MuslAttr)
+	}
+
+	target := "install"
+	script := `
+mv -v /work/lib/* /work/system/lib
+rmdir -v /work/lib/
+`
+	if attr.Headers {
+		target = "install-headers"
+		script = ""
+	}
+
+	extra := []pkg.Artifact{
+		t.NewMake(),
+	}
+	if t == toolchainStage3 {
+		extra = nil
+	}
+
+	return t.New("musl-"+version, slices.Concat(
+		attr.Extra,
+		extra,
+	), nil, slices.Concat([]string{
+		"ROSA_MUSL_TARGET=" + target,
+	}, attr.Env), `
+# expected to be writable in copies
+chmod -R +w /usr/src/musl/
+
+cd "$(mktemp -d)"
+/usr/src/musl/configure \
+	--prefix=/system \
+	--target="${ROSA_TRIPLE}"
+make "-j$(nproc)" DESTDIR=/work "${ROSA_MUSL_TARGET}"
+`+script, pkg.Path(AbsUsrSrc.Append("musl"), true, pkg.NewHTTPGetTar(
+		nil,
+		"https://musl.libc.org/releases/musl-"+version+".tar.gz",
+		mustDecode(checksum),
+		pkg.TarGzip,
+	)))
+}