devel/indi: fix build with libc++ 21
With libc++ 21 devel/indi fails to build, with errors similar to:
/wrkdirs/usr/ports/devel/indi/work/indi-2.1.7/drivers/auxiliary/gemini_flatpanel_adapters.cpp:242:14: error: use of undeclared identifier 'atoi'
242 | int id = atoi(id_str);
| ^~~~
/wrkdirs/usr/ports/devel/indi/work/indi-2.1.7/drivers/auxiliary/gemini_flatpanel_adapters.cpp:341:14: error: use of undeclared identifier 'atoi'
341 | *value = atoi(value_str);
| ^~~~
/wrkdirs/usr/ports/devel/indi/work/indi-2.1.7/drivers/auxiliary/gemini_flatpanel_adapters.cpp:658:14: error: use of undeclared identifier 'atoi'
658 | int id = atoi(id_str);
| ^~~~
/wrkdirs/usr/ports/devel/indi/work/indi-2.1.7/drivers/auxiliary/gemini_flatpanel_adapters.cpp:793:14: error: use of undeclared identifier 'atoi'
793 | *value = atoi(value_str);
| ^~~~
/wrkdirs/usr/ports/devel/indi/work/indi-2.1.7/drivers/auxiliary/gemini_flatpanel_adapters.cpp:1154:14: error: use of undeclared identifier 'atoi'
1154 | *value = atoi(value_str);
| ^~~~This is because atoi is declared in <cstdlib>, and before libc++ 21
that header got transitively included via other standard headers, but
that is no longer the case. Include <cstdlib> explicitly to fix the
errors.
PR: 293394
Approved by: acm (maintainer)
MFH: 2026Q1
(cherry picked from commit 300d6785c97c4fe8e9ee682248c4269723905ac7)