ninja backend: Fix custom_target() console: kwarg when using env

When a custom_target() uses an env, meson uses a wrapper
script to run the executable. This breaks the console: kwarg
because the wrapper script buffers the output. Fix it by setting
the verbose flag which will not buffer output.

mesonbuild/backend/ninjabackend.py

@@ -1004,7 +1004,8 @@ class NinjaBackend(backends.Backend):
                                                 extra_bdeps=target.get_transitive_build_target_deps(),
                                                 capture=ofilenames[0] if target.capture else None,
                                                 feed=srcs[0] if target.feed else None,
-                                                env=target.env)
+                                                env=target.env,
+                                                verbose=target.console)
         if reason:
             cmd_type = f' (wrapped by meson {reason})'
         else: