build: add test cmd flag -v for verbose logs (#20298)

Adds flags akin to -coverage flag enabling the test runner
to use go test's -v flag, signaling verbose test log output.

build/ci.go

@@ -318,6 +318,7 @@ func goToolArch(arch string, cc string, subcmd string, args ...string) *exec.Cmd
 
 func doTest(cmdline []string) {
 	coverage := flag.Bool("coverage", false, "Whether to record code coverage")
+	verbose := flag.Bool("v", false, "Whether to log verbosely")
 	flag.CommandLine.Parse(cmdline)
 	env := build.Env()
 
@@ -334,6 +335,9 @@ func doTest(cmdline []string) {
 	if *coverage {
 		gotest.Args = append(gotest.Args, "-covermode=atomic", "-cover")
 	}
+	if *verbose {
+		gotest.Args = append(gotest.Args, "-v")
+	}
 
 	gotest.Args = append(gotest.Args, packages...)
 	build.MustRun(gotest)