contrib/plugins/execlog: Add tab to the separator search of insn_disas

contrib/plugins/execlog: Add tab to the separator search of insn_disas

Currently, execlog searches for a space separator between the
instruction mnemonic and operands, but some disassemblers, e.g. Alpha's,
use a tab separator instead; this results in a null pointer being passed
as the haystack in g_strstr during a subsequent register search, i.e.
undefined behavior, because of a missing null check.

This patch adds tab to the separator search and a null check on the
result.

Also, an affected pointer is changed to const.

Lastly, a break statement was added to immediately terminate the
register search when a user-requested register is found in the current
instruction as a trivial optimization, because searching for the
remaining requested registers is unnecessary once one is found.

Suggested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Yodel Eldar <yodel.eldar@gmail.com>
Message-ID: <20250630164124.26315-2-yodel.eldar@gmail.com>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-ID: <20250710104531.3099313-4-alex.bennee@linaro.org>