package/autofs: fix build with glibc >= 2.34

package/autofs: fix build with glibc >= 2.34

Fix the following build failure with glibc >= 2.34:

In file included from /tmp/instance-0/output-1/host/arc-buildroot-linux-gnu/sysroot/usr/include/bits/local_lim.h:81,
                 from /tmp/instance-0/output-1/host/arc-buildroot-linux-gnu/sysroot/usr/include/bits/posix1_lim.h:161,
                 from /tmp/instance-0/output-1/host/arc-buildroot-linux-gnu/sysroot/usr/include/dirent.h:233,
                 from automount.c:22:
automount.c:87:37: error: initializer element is not constant
   87 | size_t detached_thread_stack_size = PTHREAD_STACK_MIN * 144;
      |                                     ^~~~~~~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/0c8ab8968b2adf6a5f8eeab00ce388968fa1c1d5

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>