ninja: Fix build_by_default=false targets in tests

Previously, build_by_default=false targets would not be built at all
even if they were used in a test (as the exe or as a command-line
argument) which would lead to a test failure.

Now we look into all the defined tests and add all CustomTargets and
BuildTargets used in them to the list of build_by_default targets.

mesonbuild/backend/ninjabackend.py

@@ -2161,11 +2161,28 @@ rule FORTRAN_DEP_HACK
         elem.write(outfile)
 
     def get_build_by_default_targets(self):
-        result = []
+        result = {}
+        # Get all build and custom targets that must be built by default
         for t in self.build.get_targets().values():
             if t.build_by_default or t.install or t.build_always:
-                result.append(t)
-        return result
+                result[t] = True
+        # Get all targets used as test executables and arguments. These must
+        # also be built by default. XXX: Sometime in the future these should be
+        # built only before running tests.
+        for t in self.build.get_tests():
+            exe = t.exe
+            if hasattr(exe, 'held_object'):
+                exe = exe.held_object
+            if isinstance(exe, (build.CustomTarget, build.BuildTarget)) and exe not in result:
+                result[exe] = True
+            for arg in t.cmd_args:
+                if hasattr(arg, 'held_object'):
+                    arg = arg.held_object
+                if not isinstance(arg, (build.CustomTarget, build.BuildTarget)):
+                    continue
+                if arg not in result:
+                    result[arg] = True
+        return result.keys()
 
     def generate_ending(self, outfile):
         targetlist = []