collector/dmesg: Fix dmesg variant detection

Check for all the CLI options we are going to use when deciding whether
to use the system's dmesg or the one we ship via busybox.

devlib/collector/dmesg.py

@@ -203,12 +203,16 @@ def __init__(self, target, level=LOG_LEVELS[-1], facility='kern', empty_buffer=F
             ))
         self.level = level
 
-        # Check if dmesg is the BusyBox one, or the one from util-linux in a
-        # recent version.
-        # Note: BusyBox dmesg does not support -h, but will still print the
-        # help with an exit code of 1
-        self.basic_dmesg = '--force-prefix' not in \
-                self.target.execute('dmesg -h', check_exit_code=False)
+        # Check if we have a dmesg from a recent util-linux build, rather than
+        # e.g. busybox's dmesg or the one shipped on some Android versions
+        # (toybox).  Note: BusyBox dmesg does not support -h, but will still
+        # print the help with an exit code of 1
+        help_ = self.target.execute('dmesg -h', check_exit_code=False)
+        self.basic_dmesg = not all(
+            opt in help_
+            for opt in ('--facility', '--force-prefix', '--decode', '--level')
+        )
+
         self.facility = facility
         try:
             needs_root = target.read_sysctl('kernel.dmesg_restrict')