Add -DTESTSUITE and use it from extras/build-tests/nix/build.

In particular, this disables default +F for #__SYNC__ channels.
The test suite has a "+F off" but when on 3 servers, each 75
clones are connecting, the MODE is too late and the join limit
is already reached sometimes. Causing tests to fail.

extras/build-tests/nix/build

@@ -17,7 +17,7 @@ else
 fi
 
 # -DRAWCMDLOGGING was dropped, but can be useful for debugging
-export CPPFLAGS="$CPPFLAGS -DFAKELAG_CONFIGURABLE -DNOREMOVETMP"
+export CPPFLAGS="$CPPFLAGS -DFAKELAG_CONFIGURABLE -DNOREMOVETMP -DTESTSUITE"
 
 # !! skipped for now: extras/build-tests/nix/select-config $BUILDCONFIG !!
 # !! temporary use this:

src/modules/chanmodes/floodprot.c

@@ -1205,6 +1205,12 @@ int cmodef_channel_create(Channel *channel)
 	ChannelFloodProtection *base;
 	ChannelFloodProtection *fld;
 
+#ifdef TESTSUITE
+	/* Sync channels for the test suite are exempt */
+	if (!strncasecmp(channel->name, "#__SYNC__", 9))
+		return 0;
+#endif
+
 	if (!cfg.default_profile)
 		return 0;