Update run_android_tests to exit on invalid ABI

Change-Id: I3663a5efe1f71192e69e3e04821a481043d145bb
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/67467
Commit-Queue: Aaron Knobloch <aknobloch@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Auto-Submit: Aaron Knobloch <aknobloch@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

util/run_android_tests.go

diff --git a/util/run_android_tests.go b/util/run_android_tests.go
index 48f2979..ea7e424 100644
--- a/util/run_android_tests.go
+++ b/util/run_android_tests.go
@@ -151,7 +151,7 @@
 		targetPrefix = fmt.Sprintf("aarch64-linux-android%d-", *apiLevel)
 		cmd.Env = append(cmd.Env, "GOARCH=arm64")
 	default:
-		fmt.Errorf("unknown Android ABI: %q", *abi)
+		return fmt.Errorf("unknown Android ABI: %q", *abi)
 	}
 
 	// Go's Android support requires cgo and compilers from the NDK. See