Consider nosound and novideo when keeping groups

Even when `nogroups` is not used, avoid keeping the audio and video
groups when `nosound` and `novideo` are used, respectively.

Based on @rusty-snake's suggestion:
netblue30#4603 (comment)

Relates to netblue30#4603.

src/firejail/main.c

@@ -3144,17 +3144,21 @@ int main(int argc, char **argv, char **envp) {
 			}
 
 			// add audio group
-			g = get_group_id("audio");
-			if (g) {
-				sprintf(ptr, "%d %d 1\n", g, g);
-				ptr += strlen(ptr);
+			if (!arg_nosound) {
+				g = get_group_id("audio");
+				if (g) {
+					sprintf(ptr, "%d %d 1\n", g, g);
+					ptr += strlen(ptr);
+				}
 			}
 
 			// add video group
-			g = get_group_id("video");
-			if (g) {
-				sprintf(ptr, "%d %d 1\n", g, g);
-				ptr += strlen(ptr);
+			if (!arg_novideo) {
+				g = get_group_id("video");
+				if (g) {
+					sprintf(ptr, "%d %d 1\n", g, g);
+					ptr += strlen(ptr);
+				}
 			}
 
 			// add games group

src/firejail/util.c

@@ -142,14 +142,11 @@ static void clean_supplementary_groups(gid_t gid) {
 		goto clean_all;
 
 	// clean supplementary group list
-	// allow only firejail, tty, audio, video, games
 	gid_t new_groups[MAX_GROUPS];
 	int new_ngroups = 0;
 	char *allowed[] = {
 		"firejail",
 		"tty",
-		"audio",
-		"video",
 		"games",
 		NULL
 	};
@@ -161,6 +158,16 @@ static void clean_supplementary_groups(gid_t gid) {
 		i++;
 	}
 
+	if (!arg_nosound) {
+		copy_group_ifcont("audio", groups, ngroups,
+		                  new_groups, &new_ngroups, MAX_GROUPS);
+	}
+
+	if (!arg_novideo) {
+		copy_group_ifcont("video", groups, ngroups,
+		                  new_groups, &new_ngroups, MAX_GROUPS);
+	}
+
 	if (new_ngroups) {
 		rv = setgroups(new_ngroups, new_groups);
 		if (rv)