buildtools: fix build with busybox

buildtools: fix build with busybox

If using busybox for mktemp and awk (as in Alpine),
some bugs prevent the script from running:

1/ It seems busybox mktemp requires the pattern to have at least
6 X and no other suffix.
The same has been fixed for other scripts in the past:
commit 3771edc35438 ("buildtools: fix build for some mktemp")

2/ It seems busybox awk does not accept the regex ^.*{
except if the opening curly brace is escaped.

Fixes: 4c82473412e8 ("build: add internal tag check")
Fixes: 68b1f1cda5b4 ("build: check AVX512 rather than binutils version")
Fixes: 3290ac14eb94 ("buildtools: detect discrepancies for experimental symbols")
Cc: stable@dpdk.org
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Acked-by: David Marchand <david.marchand@redhat.com>