Check for setsid respecting --wait (#595)

Author: Mic92

src/get-facts.sh

@@ -18,6 +18,6 @@ hasSudo=$(has sudo)
 hasDoas=$(has doas)
 hasWget=$(has wget)
 hasCurl=$(has curl)
-hasSetsid=$(has setsid)
+hasSetsid=$(if [ "$(has setsid)" = "y" ] && setsid --wait true 2>/dev/null; then echo "y"; else echo "n"; fi)
 hasNixOSFacter=$(command -v nixos-facter >/dev/null && echo "y" || echo "n")
 FACTS

src/nixos-anywhere.sh

@@ -993,7 +993,7 @@ main() {
   fi
 
   if [[ ${hasSetsid-n} == "n" ]]; then
-    abort "no setsid command found, but required to run the kexec script under a new session"
+    abort "no setsid command respecting --wait found, but required to run the kexec script under a new session"
   fi
 
   if [[ ${isOs} != "Linux" ]]; then