When the system does not provide a compress executable, we use our
own. Before, this was done by installing an executable named
'compress' along with Gash. This commit allows the compressed-port
functions to use our built-in compress without needing an external
executable.
* gash/config.scm.in (exec-internal-compress): New function.
(%compress): Fall back to it on systems without compress.
* gash/guix-utils.scm (filtered-port, filtered-output-port): When the
given command list begins with a procedure, apply it to its arguments
instead of using execl.
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