buildutil: update tests for new "unix" build constraint

buildutil_test.go

@@ -549,6 +549,19 @@ var goodOSArchFileTests = []goodOSArchFileTest{
 		tags:     []string{"darwin", "arm64"},
 		match:    false,
 	},
+	// TODO: for now the "unix" build constraint is not applied to file names
+	{
+		GOOS:     "darwin",
+		GOARCH:   "arm64",
+		filename: "syscall_unix.go",
+		match:    true,
+	},
+	{
+		GOOS:     "windows",
+		GOARCH:   "amd64",
+		filename: "syscall_unix.go",
+		match:    true,
+	},
 }
 
 func init() {

file.go

@@ -22,8 +22,7 @@ import (
 //
 // An exception: if GOOS=android, then files with GOOS=linux are also matched.
 func goodOSArchFile(ctxt *build.Context, name string, allTags map[string]bool) bool {
-	// TODO: check if name contains path elements?
-	name, _, _ = cut(name, ".")
+	name, _, _ = strings.Cut(name, ".")
 
 	// Before Go 1.4, a file called "linux.go" would be equivalent to having a
 	// build tag "linux" in that file. For Go 1.4 and beyond, we require this