mesontest: Use test setup name in logfiles

When using a setup, use the setup name as the namebase for the logfile
instead of the wrapper. The wrapper may not be set, or it may be shared
between test setups.

Also don't try to use the wrapper if it's an empty list.

Closes https://github.com/mesonbuild/meson/issues/1371

mesontest.py

@@ -415,15 +415,18 @@ TIMEOUT: %4d
         if not self.options.logbase or self.options.verbose:
             return None, None, None, None
 
+        namebase = None
         logfile_base = os.path.join(self.options.wd, 'meson-logs', self.options.logbase)
 
-        if self.options.wrapper is None:
-            logfilename = logfile_base + '.txt'
-            jsonlogfilename = logfile_base + '.json'
-        else:
+        if self.options.wrapper:
             namebase = os.path.split(self.get_wrapper()[0])[1]
-            logfilename = logfile_base + '-' + namebase.replace(' ', '_') + '.txt'
-            jsonlogfilename = logfile_base + '-' + namebase.replace(' ', '_') + '.json'
+        elif self.options.setup:
+            namebase = self.options.setup
+
+        if namebase:
+            logfile_base += '-' + namebase.replace(' ', '_')
+        logfilename = logfile_base + '.txt'
+        jsonlogfilename = logfile_base + '.json'
 
         jsonlogfile = open(jsonlogfilename, 'w')
         logfile = open(logfilename, 'w')