internal/rosa: chmod via patch helper

This works around the zfs overlay mount overhead and significantly reduces I/O in general.

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

internal/rosa/musl.go

@@ -48,18 +48,17 @@ rmdir -v /work/lib
 	), 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,
+`+script, pkg.Path(AbsUsrSrc.Append("musl"), false, t.NewPatchedSource(
+		// expected to be writable in copies
+		"musl", version, pkg.NewHTTPGetTar(
+			nil, "https://musl.libc.org/releases/musl-"+version+".tar.gz",
+			mustDecode(checksum),
+			pkg.TarGzip,
+		), false,
 	)))
 }