Update minimal-init

Co-authored-by: James Le Cuirot <[email protected]>

Author: pothos

minimal-init

@@ -152,10 +152,12 @@ elif [ "${usrfstype}" = btrfs ] || [ "${usrfstype}" = auto ]; then
   fi
 fi
 # Only proceed if the source is a path.
-if echo "${usr}" | grep -v -q "^/"; then
-  echo "No mountable /usr partition given (usr='${usr}')" >&2
-  false # Throw error
-fi
+case "${usr}" in
+  /*) : ;;
+  *) echo "No mountable /usr partition given (usr='${usr}')" >&2
+    false # Throw error
+    ;;
+esac
 
 debug_sh 3/4: before /sysusr mount