gosh: Stop special-casing propagate output in BuildGoPkg

I'd originally overridden PropagateOutput to false in
BuildGoPkg because "go build" was spewing lots of useless
output, which interfered with debugging using
PropagateChildOutput=true, but today I realized the spew was
because of the -x flag, which we need not set. So, we stop
setting -x and drop the special-casing.

Change-Id: If17ee00c1263cc51bb27bf7bdea7caff084757f4
diff --git a/gosh/shell.go b/gosh/shell.go
index 4dbcc51..637c7ce 100644
--- a/gosh/shell.go
+++ b/gosh/shell.go
@@ -372,14 +372,13 @@
 	}
 	defer os.RemoveAll(tempDir)
 	tempBinPath := filepath.Join(tempDir, path.Base(pkg))
-	args := []string{"build", "-x", "-o", tempBinPath}
+	args := []string{"build", "-o", tempBinPath}
 	args = append(args, flags...)
 	args = append(args, pkg)
 	c, err := sh.cmd(nil, "go", args...)
 	if err != nil {
 		return "", err
 	}
-	c.PropagateOutput = false
 	if err := c.run(); err != nil {
 		return "", err
 	}