Newbie developer: /bin/sh sees command with arguments as name for binary

[Julian Groß <julian g posteo de>]

    Hello,
      
      I am in the process of adding multi-threaded support to
      file-roller. Unfortunately I have run into a weird problem where
      the command that gets generated for `tar` works in terminal but
      not inside file-roller. Somehow /bin/sh seems to interpret
      whatever you give to --use-compress-program="" as a binary rather
      than a binary and an argument.
      This is what I currently have:
      https://gitlab.gnome.org/jug007/file-roller/-/merge_requests/1/diffs
      The lbzip2 code at line 217 in src/fr-command-tar.c is what I am
      currently working with. Compressing something to tar.bz2 with
      lbzip2 installed fails since /bin/sh cannot find the command
      "lbzip2 -n 1".
      The code for actually running the command seems to be in
      src/fr-process.c line 944, but I cannot really make any sense of
      it. I am pretty much a complete newbie and this is my first time
      working on a program in C.
      I would appreciate if someone could take a look at the code and
      see if they can find out what is going wrong.
      
      By the way, and example command that is generated by file-roller
      is:
      tar --force-local --no-recursion --no-wildcards -v -p -C
      /home/motofckr9k/osc/home:JulianGro/vircadia-domain -cf
/home/motofckr9k/osc/home:JulianGro/vircadia-domain/.fr-F2ZXj4/vircadia-2021.1.0.tar.bz2
      --use-compress-program='lbzip2 -n 1' -T
      /home/motofckr9k/.cache/.fr-Wc4QJ1/file-list --
      
      Error message is:
      /bin/sh: 1: lbzip2 -n 1: not found
      
      
      Greetings
      Julian Groß