internal/rosa: isolate patching helper

This is useful outside llvm as well.

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

internal/rosa/llvm.go

@@ -170,34 +170,14 @@ cp -r /system/include /usr/include && rm -rf /system/include
 		)
 	}
 
-	source := pkg.NewHTTPGetTar(
-		nil, "https://github.com/llvm/llvm-project/archive/refs/tags/"+
-			"llvmorg-"+version+".tar.gz",
-		mustDecode(checksum),
-		pkg.TarGzip,
-	)
-
-	patches := make([]pkg.ExecPath, len(attr.patches)+1)
-	for i, p := range attr.patches {
-		patches[i+1] = pkg.Path(
-			AbsUsrSrc.Append("llvm-patches", p[0]+".patch"), false,
-			pkg.NewFile(p[0], []byte(p[1])),
-		)
-	}
-	patches[0] = pkg.Path(AbsUsrSrc.Append("llvmorg"), false, source)
-	if len(patches) > 1 {
-		source = t.New(
-			"llvmorg-patched", stage3Concat(t, []pkg.Artifact{},
-				t.Load(Patch),
-			), nil, nil, `
-cp -r /usr/src/llvmorg/. /work/.
-chmod -R +w /work && cd /work
-cat /usr/src/llvm-patches/* | patch -p 1
-`, patches...,
-		)
-	}
-
-	return t.NewViaCMake("llvm", version, variant, source, &CMakeAttr{
+	return t.NewViaCMake("llvm", version, variant, t.NewPatchedSource(
+		"llvmorg", pkg.NewHTTPGetTar(
+			nil, "https://github.com/llvm/llvm-project/archive/refs/tags/"+
+				"llvmorg-"+version+".tar.gz",
+			mustDecode(checksum),
+			pkg.TarGzip,
+		), true, attr.patches...,
+	), &CMakeAttr{
 		Cache:  slices.Concat(cache, attr.cmake),
 		Append: cmakeAppend,
 		Extra: stage3Concat(t, attr.extra,