cmd/go: convert TestGoBuildNotMain to script framework

Part of converting all tests to script framework to improve
test parallelism.

Updates #36320
Updates #17751

Change-Id: Icd62dc8db55bec52ad326bc370ee7e435aae2559
Reviewed-on: https://go-review.googlesource.com/c/go/+/212812
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/go_test.go

@@ -1799,16 +1799,6 @@ func TestGoTestMutexprofileDashOControlsBinaryLocation(t *testing.T) {
 	tg.wantExecutable("myerrors.test"+exeSuffix, "go test -mutexprofile -o myerrors.test did not create myerrors.test")
 }
 
-func TestGoBuildNonMain(t *testing.T) {
-	tg := testgo(t)
-	defer tg.cleanup()
-	// TODO: tg.parallel()
-	tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
-	tg.runFail("build", "-buildmode=exe", "-o", "not_main"+exeSuffix, "not_main")
-	tg.grepStderr("-buildmode=exe requires exactly one main package", "go build with -o and -buildmode=exe should on a non-main package should throw an error")
-	tg.mustNotExist("not_main" + exeSuffix)
-}
-
 func TestGoTestDashCDashOControlsBinaryLocation(t *testing.T) {
 	skipIfGccgo(t, "gccgo has no standard packages")
 	tooSlow(t)

src/cmd/go/testdata/script/build_exe.txt

+# go build with -o and -buildmode=exe should on a non-main package should throw an error
+
+! go build -buildmode=exe -o out$GOEXE not_main
+stderr '-buildmode=exe requires exactly one main package'
+! exists out$GOEXE
+! go build -buildmode=exe -o out$GOEXE main_one main_two
+stderr '-buildmode=exe requires exactly one main package'
+! exists out$GOEXE
+
+-- not_main/not_main.go --
+package not_main
+
+func F() {}
+-- main_one/main_one.go --
+package main
+
+func main() {}
+-- main_two/main_two.go --
+package main
+
+func main() {}
\ No newline at end of file

src/cmd/go/testdata/src/not_main/not_main.go

-package not_main
-
-func F() {}