internal/linker: patch each major Go version separately

Go 1.21 already breaks one of the three patches.
The complexity of the patches will likely increase,
and we only ever need to actively maintain the highest set of patches,
so splitting by major version feels natural.

internal/linker/linker.go

@@ -33,19 +33,16 @@ const (
 	baseSrcSubdir  = "src"
 )
 
-//go:embed patches/*.patch
+//go:embed patches/*/*.patch
 var linkerPatchesFS embed.FS
 
-func loadLinkerPatches() (version string, modFiles map[string]bool, patches [][]byte, err error) {
+func loadLinkerPatches(majorGoVersion string) (version string, modFiles map[string]bool, patches [][]byte, err error) {
 	modFiles = make(map[string]bool)
 	versionHash := sha256.New()
-	err = fs.WalkDir(linkerPatchesFS, ".", func(path string, d fs.DirEntry, err error) error {
-		if err != nil {
+	if err := fs.WalkDir(linkerPatchesFS, "patches/"+majorGoVersion, func(path string, d fs.DirEntry, err error) error {
+		if err != nil || d.IsDir() {
 			return err
 		}
-		if d.IsDir() {
-			return nil
-		}
 
 		patchBytes, err := linkerPatchesFS.ReadFile(path)
 		if err != nil {
@@ -68,10 +65,8 @@ func loadLinkerPatches() (version string, modFiles map[string]bool, patches [][]
 		}
 		patches = append(patches, patchBytes)
 		return nil
-	})
-
-	if err != nil {
-		return
+	}); err != nil {
+		return "", nil, nil, err
 	}
 	version = base64.RawStdEncoding.EncodeToString(versionHash.Sum(nil))
 	return
@@ -230,7 +225,11 @@ func buildLinker(workingDir string, overlay map[string]string, outputLinkPath st
 }
 
 func PatchLinker(goRoot, goVersion, tempDir string) (string, func(), error) {
-	patchesVer, modFiles, patches, err := loadLinkerPatches()
+	// rxVersion looks for a version like "go1.19" or "go1.20"
+	rxVersion := regexp.MustCompile(`go\d+\.\d+`)
+	majorGoVersion := rxVersion.FindString(goVersion)
+
+	patchesVer, modFiles, patches, err := loadLinkerPatches(majorGoVersion)
 	if err != nil {
 		panic(fmt.Errorf("cannot retrieve linker patches: %v", err))
 	}