[openssl/openssl] 9607f5: Fix handling of the "0:" label in arm-xlate.pl

[Tom Cosgrove]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: 9607f5ccf285ac9988a86f95c5ad9f92b556a843
      https://github.com/openssl/openssl/commit/9607f5ccf285ac9988a86f95c5ad9f92b556a843
  Author: Tom Cosgrove <tom.cosgrove at arm.com>
  Date:   2023-08-08 (Tue, 08 Aug 2023)

  Changed paths:
    M crypto/perlasm/arm-xlate.pl

  Log Message:
  -----------
  Fix handling of the "0:" label in arm-xlate.pl

When $label == "0", $label is not truthy, so `if ($label)` thinks there isn't
a label. Correct this by looking at the result of the s/// command.

Verified that there are no changes in the .S files created during a normal
build, and that the "0:" labels appear in the translation given in the error
report (and they are the only difference in the before and after output).

Fixes #21647

Change-Id: I5f2440100c62360bf4bdb7c7ece8dddd32553c79

Reviewed-by: Paul Dale <pauli at openssl.org>
Reviewed-by: Shane Lontis <shane.lontis at oracle.com>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21653)