cmd/go: fix build

Failures noted by dashboard.

Change-Id: I22f90120c6687b64b9efff9df7a7fa8f26d24bac
Reviewed-on: https://go-review.googlesource.com/12207Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/go/build.go

@@ -719,7 +719,7 @@ func goFilesPackage(gofiles []string) *Package {
 		}
 		dir1, _ := filepath.Split(file)
 		if dir1 == "" {
-			dir1 = "."
+			dir1 = "./"
 		}
 		if dir == "" {
 			dir = dir1

src/cmd/go/go_test.go

@@ -2081,9 +2081,9 @@ func TestGoRunDirs(t *testing.T) {
 	defer tg.cleanup()
 	tg.cd("testdata/rundir")
 	tg.runFail("run", "x.go", "sub/sub.go")
-	tg.grepStderr("named files must all be in one directory; have . and sub/", "wrong output")
+	tg.grepStderr("named files must all be in one directory; have ./ and sub/", "wrong output")
 	tg.runFail("run", "sub/sub.go", "x.go")
-	tg.grepStderr("named files must all be in one directory; have sub/ and .", "wrong output")
+	tg.grepStderr("named files must all be in one directory; have sub/ and ./", "wrong output")
 }
 
 func TestGoInstallPkgdir(t *testing.T) {
@@ -2099,6 +2099,13 @@ func TestGoInstallPkgdir(t *testing.T) {
 }
 
 func TestGoTestRaceInstallCgo(t *testing.T) {
+	switch sys := runtime.GOOS + "/" + runtime.GOARCH; sys {
+	case "darwin/amd64", "freebsd/amd64", "linux/amd64", "windows/amd64":
+		// ok
+	default:
+		t.Skip("no race detector on %s", sys)
+	}
+
 	// golang.org/issue/10500.
 	// This used to install a race-enabled cgo.
 	tg := testgo(t)

src/cmd/go/testdata/src/testdep/p1/p1.go

+package p1

src/cmd/go/testdata/src/testdep/p1/p1_test.go

+package p1
+
+import _ "testdep/p2"

src/cmd/go/testdata/src/testdep/p2/p2.go

+package p2
+
+import _ "testdep/p3"

src/cmd/go/testdata/src/testdep/p3/p3.go

+// +build ignore
+
+package ignored