Enable use of the TestCase driver infr with instr warnings

We do that by adding an optional tolerate_messages parameter to the
TestCase constructor and passing it down to gnatcov instrument
invocations.

Author: Jugst3r

testsuite/SCOV/internals/driver.py

@@ -1301,7 +1301,8 @@ def mode_build(self):
             dump_trigger=self.dump_trigger,
             gprsw=instrument_gprsw,
             gpr_obj_dir=self.gpr_obj_dir,
-            out=out)
+            out=out,
+            tolerate_messages=self.testcase.tolerate_messages)
 
         # When exception propagation is not available, a test ending with an
         # unhandled exception goes straight to the last_chance_handler from
@@ -1328,11 +1329,12 @@ def mode_build(self):
         # Standard output might contain warnings indicating instrumentation
         # issues. This should not happen, so simply fail as soon as the output
         # file is not empty.
-        thistest.fail_if(
-            os.path.getsize(out) > 0,
-            'xcov instrument standard output not empty ({}):'
-            '\n--'
-            '\n{}'.format(out, contents_of(out)))
+        if not self.testcase.tolerate_messages:
+            thistest.fail_if(
+                os.path.getsize(out) > 0,
+                'xcov instrument standard output not empty ({}):'
+                '\n--'
+                '\n{}'.format(out, contents_of(out)))
 
         # Now we can build, instructing gprbuild to fetch the instrumented
         # sources in their dedicated subdir:

testsuite/SCOV/tc.py

@@ -123,11 +123,16 @@ def __drivers_from(self, cspec):
         # match this expression
         return [drv for drv in self.all_drivers if re.search(drv_expr, drv)]
 
-    def __init__(self, extradrivers="", extracargs="", category=CAT.auto):
+    def __init__(self, extradrivers="", extracargs="", category=CAT.auto,
+                 tolerate_messages=None):
         # By default, these test cases expect no error from subprocesses (xrun,
         # xcov, etc.)
         self.expect_failures = False
 
+        # Pass tolerate_messages to gnatcov instrument invocations (see the doc
+        # for xcov_instrument).
+        self.tolerate_messages = tolerate_messages
+
         # Step 1: Compute the list of drivers and consolidation specs
         #         to exercise
         # ------------------------------------------------------------