cmd/go: fix the rebuilding stale packages test

Non-main packages do not depend on the "runtime" package,
but main packages still do. Use a main package in the test.

This change passes the -i flag to the install command
to allow installation of updated dependencies,
and removes "install std" as unnecessary.

https://golang.org/cl/107957 is relevant to fixed test.

Updates #24436

Change-Id: If1845f37581a16ad77e72e50be21010e198bc7c5
Reviewed-on: https://go-review.googlesource.com/103675Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/go_test.go

@@ -895,9 +895,11 @@ func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
 		}
 	}
 
-	tg.tempFile("d1/src/p1/p1.go", `package p1`)
+	// Every main package depends on the "runtime".
+	tg.tempFile("d1/src/p1/p1.go", `package main; func main(){}`)
 	tg.setenv("GOPATH", tg.path("d1"))
-	tg.run("install", "-a", "p1")
+	// Pass -i flag to rebuild everything outdated.
+	tg.run("install", "-i", "p1")
 	tg.wantNotStale("p1", "", "./testgo list claims p1 is stale, incorrectly, before any changes")
 
 	// Changing mtime of runtime/internal/sys/sys.go
@@ -919,13 +921,13 @@ func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
 	tg.wantNotStale("p1", "", "./testgo list claims p1 is stale, incorrectly, after changing back to old release")
 	addNL(sys)
 	tg.wantStale("p1", "stale dependency: runtime/internal/sys", "./testgo list claims p1 is NOT stale, incorrectly, after changing sys.go again")
-	tg.run("install", "p1")
+	tg.run("install", "-i", "p1")
 	tg.wantNotStale("p1", "", "./testgo list claims p1 is stale after building with new release")
 
 	// Restore to "old" release.
 	restore()
 	tg.wantStale("p1", "stale dependency: runtime/internal/sys", "./testgo list claims p1 is NOT stale, incorrectly, after restoring sys.go")
-	tg.run("install", "p1")
+	tg.run("install", "-i", "p1")
 	tg.wantNotStale("p1", "", "./testgo list claims p1 is stale after building with old release")
 
 	// Everything is out of date. Rebuild to leave things in a better state.