os/exec, syscall: fix tests to pass when GOGCTRACE=1 is set

R=golang-dev, bradfitz, minux.ma
CC=golang-dev
https://golang.org/cl/8193043

src/pkg/os/exec/exec_test.go

@@ -25,7 +25,7 @@ func helperCommand(s ...string) *Cmd {
 	cs := []string{"-test.run=TestHelperProcess", "--"}
 	cs = append(cs, s...)
 	cmd := Command(os.Args[0], cs...)
-	cmd.Env = append([]string{"GO_WANT_HELPER_PROCESS=1"}, os.Environ()...)
+	cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1"}
 	return cmd
 }
 

src/pkg/syscall/passfd_test.go

@@ -49,7 +49,7 @@ func TestPassFD(t *testing.T) {
 	defer readFile.Close()
 
 	cmd := exec.Command(os.Args[0], "-test.run=^TestPassFD$", "--", tempDir)
-	cmd.Env = append([]string{"GO_WANT_HELPER_PROCESS=1"}, os.Environ()...)
+	cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1"}
 	cmd.ExtraFiles = []*os.File{writeFile}
 
 	out, err := cmd.CombinedOutput()