Change 'ensure-directories-exist' to look for 'mkdir' in $PATH, not in /bin.

--- maxima-5.36.1/lisp-utils/defsystem.lisp.orig	2014-11-22 16:21:30.000000000 -0500
+++ maxima-5.36.1/lisp-utils/defsystem.lisp	2015-05-25 21:53:31.223648483 -0400
@@ -4627,7 +4627,7 @@
         (cmd (if (member :win32 *features*)
                  (format nil "mkdir \"~a\""
                          (coerce (subst #\\ #\/ (coerce (namestring dir) 'list)) 'string))
-                 (format nil "/bin/mkdir -p ~S" (namestring dir)))))
+                 (format nil "mkdir -p ~S" (namestring dir)))))
    (unless (directory dir)
      (lisp:system cmd))
    ;; The second return value is supposed to be T if directories were
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<tr><td><span title='2023-06-17 14:38:32 +0200'>2023-06-17</span></td><td><a href='/guix/commit/gnu/packages/attr.scm?id=ff690faf66d8f37ee6b679fcb7cf37e369624ee3'>gnu: Use target-hurd?, system-hurd? instead of hurd-target?, hurd-system?.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/hurd.scm (hurd-target?): Remove.
(hurd-system?): Move to...
* guix/utils.scm (system-hurd?): ...here.
* gnu/packages/*: Update all users, removing (gnu packages hurd) include where
now unused.
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>
<tr><td><span title='2021-09-14 15:49:56 +0200'>2021-09-14</span></td><td><a href='/guix/commit/gnu/packages/attr.scm?id=49ab267cbec17643e265305c109dc397b5e43cf5'>gnu: attr: Allow compilation on GNU/Hurd.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/attr.scm (attr)[arguments]: Add 'skip-linux-syscalls'
phase when 'hurd-target?' returns true.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-07-23 17:26:45 +0200'>2021-07-23</span></td><td><a href='/guix/commit/gnu/packages/attr.scm?id=e045fd7ce22fb0c098db8317e4e06b68c543ba60'>gnu: attr: Update to 2.5.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/attr.scm (attr): Update to 2.5.1.
[arguments]: Remove trailing #t.
</span></span></td><td>Marius Bakke</td></tr>