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/python.go

@@ -47,9 +47,6 @@ func (t Toolchain) newPython() pkg.Artifact {
 		"LDFLAGS=-Wl,--dynamic-linker=/system/lib/" +
 			"ld-musl-" + linuxArch() + ".so.1",
 	}, `
-# test_synopsis_sourceless assumes this is writable and checks __pycache__
-chmod -R +w /usr/src/python/
-
 export HOME="$(mktemp -d)"
 cd "$(mktemp -d)"
 /usr/src/python/configure \
@@ -59,12 +56,13 @@ make "-j$(nproc)"
 make test
 make DESTDIR=/work install
 `, pkg.Path(AbsUsrSrc.Append("python"), true,
-		pkg.NewHTTPGetTar(
+		// test_synopsis_sourceless assumes this is writable and checks __pycache__
+		t.NewPatchedSource("python", version, pkg.NewHTTPGetTar(
 			nil, "https://www.python.org/ftp/python/"+version+
 				"/Python-"+version+".tgz",
 			mustDecode(checksum),
 			pkg.TarGzip,
-		)))
+		), false)))
 }
 func init() { artifactsF[Python] = Toolchain.newPython }