Defend fingerprint against even-smarter LTO

* src/pdumper.c (Fdump_emacs_portable, pdumper_load):
Don’t cast volatile to non-volatile pointer, as that does not in
general suffice to prevent a compiler from optimizing away memcmp
and/or memcpy calls.  Instead, copy the fingerprint by hand.
1 job for master in 90 minutes and 1 second (queued for 6 seconds)
Status Job ID Name Coverage
  Test
failed #2470
test-all

01:30:01

 
Name Stage Failure
failed
test-all Test The script exceeded the maximum execution time set for the job
  GEN      lisp/international/ccl-tests.log
ELC lisp/international/mule-tests.elc
GEN lisp/international/mule-tests.log
ELC lisp/international/mule-util-tests.elc
GEN lisp/international/mule-util-tests.log
ELC lisp/international/ucs-normalize-tests.elc
GEN lisp/international/ucs-normalize-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-f100a208 ...
ERROR: Job failed: execution took longer than 1h30m0s seconds