pack: Move absolute file name to <compressor>.

* guix/scripts/pack.scm (<compressor>)[package]: Remove.
[command]: Document as being a gexp with an absolute file name.
(%compressors): Adjust accordingly.
(self-contained-tarball): Simplify PATH expression.  Move 'string-join'
for the compressor command on the build side.
(docker-image): Simplify PATH expression.
* tests/pack.scm (%gzip-compressor): Adjust accordingly.

1 files changed, 2 insertions, 1 deletions

diff --git a/tests/pack.scm b/tests/pack.scm
index de9ef8e6ab3..eb643c3229f 100644
--- a/tests/pack.scm
+++ b/tests/pack.scm
@@ -42,7 +42,8 @@
 (define %gzip-compressor
   ;; Compressor that uses the bootstrap 'gzip'.
   ((@ (guix scripts pack) compressor) "gzip"
-   %bootstrap-coreutils&co "gz" '("gzip" "-6n")))
+   "gz"
+   #~(#+(file-append %bootstrap-coreutils&co "/bin/gzip") "-6n")))
 
 (define %tar-bootstrap %bootstrap-coreutils&co)