Remove fixed search paths from autotools.

--- a/m4/package_utilies.m4	1970-01-01 01:00:01.000000000 +0100
+++ b/m4/package_utilies.m4	2020-07-07 12:41:48.871661042 +0200
@@ -23,32 +23,32 @@
     AC_PACKAGE_NEED_UTILITY($1, "$cc", cc, [C compiler])
 
     if test -z "$MAKE"; then
-        AC_PATH_PROG(MAKE, gmake,, /usr/bin:/usr/freeware/bin)
+        AC_PATH_PROG(MAKE, gmake)
     fi
     if test -z "$MAKE"; then
-        AC_PATH_PROG(MAKE, make,, /usr/bin)
+        AC_PATH_PROG(MAKE, make)
     fi
     make=$MAKE
     AC_SUBST(make)
     AC_PACKAGE_NEED_UTILITY($1, "$make", make, [GNU make])
 
     if test -z "$LIBTOOL"; then
-	AC_PATH_PROG(LIBTOOL, glibtool,, /usr/bin)
+	AC_PATH_PROG(LIBTOOL, glibtool)
     fi
     if test -z "$LIBTOOL"; then
-	AC_PATH_PROG(LIBTOOL, libtool,, /usr/bin:/usr/local/bin:/usr/freeware/bin)
+	AC_PATH_PROG(LIBTOOL, libtool)
     fi
     libtool=$LIBTOOL
     AC_SUBST(libtool)
     AC_PACKAGE_NEED_UTILITY($1, "$libtool", libtool, [GNU libtool])
 
     if test -z "$TAR"; then
-        AC_PATH_PROG(TAR, tar,, /usr/freeware/bin:/bin:/usr/local/bin:/usr/bin)
+        AC_PATH_PROG(TAR, tar)
     fi
     tar=$TAR
     AC_SUBST(tar)
     if test -z "$ZIP"; then
-        AC_PATH_PROG(ZIP, gzip,, /bin:/usr/local/bin:/usr/freeware/bin)
+        AC_PATH_PROG(ZIP, gzip)
     fi
 
     zip=$ZIP
@@ -61,25 +61,25 @@
     AC_SUBST(makedepend)
 
     if test -z "$AWK"; then
-        AC_PATH_PROG(AWK, awk,, /bin:/usr/bin)
+        AC_PATH_PROG(AWK, awk)
     fi
     awk=$AWK
     AC_SUBST(awk)
 
     if test -z "$SED"; then
-        AC_PATH_PROG(SED, sed,, /bin:/usr/bin)
+        AC_PATH_PROG(SED, sed)
     fi
     sed=$SED
     AC_SUBST(sed)
 
     if test -z "$ECHO"; then
-        AC_PATH_PROG(ECHO, echo,, /bin:/usr/bin)
+        AC_PATH_PROG(ECHO, echo)
     fi
     echo=$ECHO
     AC_SUBST(echo)
 
     if test -z "$SORT"; then
-        AC_PATH_PROG(SORT, sort,, /bin:/usr/bin)
+        AC_PATH_PROG(SORT, sort)
     fi
     sort=$SORT
     AC_SUBST(sort)
value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=4a1b3830a8ff6b05ad9a2b27c8a2cdbd00a45787'>root</a>/<a href='/guix/log/gnu?id=4a1b3830a8ff6b05ad9a2b27c8a2cdbd00a45787'>gnu</a>/<a href='/guix/log/gnu/services?id=4a1b3830a8ff6b05ad9a2b27c8a2cdbd00a45787'>services</a>/<a href='/guix/log/gnu/services/file-sharing.scm?id=4a1b3830a8ff6b05ad9a2b27c8a2cdbd00a45787'>file-sharing.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/services/file-sharing.scm?id=4a1b3830a8ff6b05ad9a2b27c8a2cdbd00a45787&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-08-25 00:10:32 -0400'>2022-08-25</span></td><td><a href='/guix/commit/gnu/services/file-sharing.scm?id=ee08277a70d29b6d707524a4e17620f50b87adf4'>services: Use the new maybe/unset API.</a><span class='msg-avail'>...</span></td><td>Attila Lendvai</td></tr>
<tr><td><span title='2022-08-01 12:49:35 -0400'>2022-08-01</span></td><td><a href='/guix/commit/gnu/services/file-sharing.scm?id=a2b89a3319dc1d621c546855f578acae5baaf6da'>services: configuration: Step back from *unspecified*.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-06-15 00:25:21 +0200'>2022-06-15</span></td><td><a href='/guix/commit/gnu/services/file-sharing.scm?id=8cb1a49a3998c39f315a4199b7d4a121a6d66449'>services: configuration: Use *unspecified* instead of 'disabled.</a><span class='msg-avail'>...</span></td><td>Attila Lendvai</td></tr>