debug: Tolerate more whitespace from OpenOCD CLI

During the github workflow this character is \n, while on my computer
it's ' '. I'm sure there's a good reason for that, but it doesn't seem
worth figuring out what that reason is.

debug/testlib.py

@@ -432,7 +432,7 @@ def command(self, cmd):
         self.command_count += 1
         self.process.stdin.write(magic + b"\n")
         self.process.stdin.flush()
-        m = self.expect(rb"(.*)^> " + re.escape(magic))
+        m = self.expect(rb"(.*)^>\s*" + re.escape(magic))
         return m.group(1)
 
     def expect(self, regex, message=None):