Regres: Adjust exit code handling

The go docs say the exit code is clobbered by `-1` on abnormal exit, but
what they don't say is there's some type mangling along the way so we
see it as 255

Bug: b/144426261
Change-Id: Ife77a950e4739afc94b9f5a950a06f4b853708ae
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38989
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>
diff --git a/tests/regres/deqp/deqp.go b/tests/regres/deqp/deqp.go
index b6b7b38..7d7acd4 100644
--- a/tests/regres/deqp/deqp.go
+++ b/tests/regres/deqp/deqp.go
@@ -252,7 +252,7 @@
 		// Don't treat non-zero error codes as crashes.
 		var exitErr *exec.ExitError
 		if errors.As(err, &exitErr) {
-			if exitErr.ExitCode() != -1 {
+			if exitErr.ExitCode() != 255 {
 				out += fmt.Sprintf("\nProcess terminated with code %d", exitErr.ExitCode())
 				err = nil
 			}