modif: keep pipewire group unless nosound is used

This group is apparently used on Gentoo[1].

Currently only the "audio" supplementary group is kept.

Fixes netblue30#5992.

See also commit f329386 ("Keep vglusers group unless no3d is used
(virtualgl)", 2022-01-07) / PR netblue30#4851.

[1] https://wiki.gentoo.org/wiki/PipeWire

Reported-by: @amano-kenji

src/firejail/main.c

@@ -3224,6 +3224,11 @@ int main(int argc, char **argv, char **envp) {
 					sprintf(ptr, "%d %d 1\n", g, g);
 					ptr += strlen(ptr);
 				}
+				g = get_group_id("pipewire");
+				if (g) {
+					sprintf(ptr, "%d %d 1\n", g, g);
+					ptr += strlen(ptr);
+				}
 			}
 
 			// add video group

src/firejail/util.c

@@ -207,6 +207,8 @@ static void clean_supplementary_groups(gid_t gid) {
 	if (!arg_nosound) {
 		copy_group_ifcont("audio", groups, ngroups,
 		                  new_groups, &new_ngroups, MAX_GROUPS);
+		copy_group_ifcont("pipewire", groups, ngroups,
+		                  new_groups, &new_ngroups, MAX_GROUPS);
 	}
 
 	if (!arg_novideo) {