Also unassign GOROOT in run-builder

Author: dagood

eng/_util/buildutil/buildutil.go

@@ -104,3 +104,19 @@ func AppendExperimentEnv(experiment string) {
 		panic(err)
 	}
 }
+
+// UnassignGOROOT unsets the GOROOT env var if it is set.
+//
+// Setting GOROOT explicitly in the environment has not been necessary since Go
+// 1.9 (https://go.dev/doc/go1.9#goroot), but a dev or build machine may still
+// have it set. It interferes with attempts to run the built Go (such as when
+// building the race runtime), so remove the explicit GOROOT if set.
+func UnassignGOROOT() error {
+	if explicitRoot, ok := os.LookupEnv("GOROOT"); ok {
+		fmt.Printf("---- Removing explicit GOROOT from environment: %v\n", explicitRoot)
+		if err := os.Unsetenv("GOROOT"); err != nil {
+			return err
+		}
+	}
+	return nil
+}

eng/_util/cmd/build/build.go

@@ -138,15 +138,8 @@ func build(o *options) error {
 	}
 	fmt.Printf("---- Target platform: %v_%v\n", targetOS, targetArch)
 
-	// Setting GOROOT explicitly in the environment has not been necessary since Go 1.9
-	// (https://go.dev/doc/go1.9#goroot), but a dev or build machine may still have it set. It
-	// interferes with attempts to run the built Go (such as when building the race runtime), so
-	// remove the explicit GOROOT if set.
-	if explicitRoot, ok := os.LookupEnv("GOROOT"); ok {
-		fmt.Printf("---- Removing explicit GOROOT from environment: %v\n", explicitRoot)
-		if err := os.Unsetenv("GOROOT"); err != nil {
-			return err
-		}
+	if err := buildutil.UnassignGOROOT(); err != nil {
+		return err
 	}
 
 	// The upstream build scripts in {repo-root}/src require your working directory to be src, or

eng/_util/cmd/run-builder/run-builder.go

@@ -105,6 +105,10 @@ func main() {
 		env("GO_TEST_TIMEOUT_SCALE", strconv.Itoa(timeoutScale))
 	}
 
+	if err := buildutil.UnassignGOROOT(); err != nil {
+		log.Fatal(err)
+	}
+
 	buildCmdline := []string{"pwsh", "eng/run.ps1", "build"}
 
 	// run.ps1 compiles Go code, so we can't use the experiment yet. We must pass the experiment