Why can't gitlab-runner see some files?

Question

git

I use the php-amqplib library in the project, which needs the php-bcmath extension.
The extension is naturally installed, but gitlab-runner stubbornly refuses to see it, but sometimes it works correctly.
Issues

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - php-amqplib/php-amqplib v2.6.3 requires ext-bcmath * -> the requested PHP extension bcmath is missing from your system.
    - php-amqplib/php-amqplib v2.6.2 requires ext-bcmath * -> the requested PHP extension bcmath is missing from your system.
    - php-amqplib/php-amqplib v2.6.1 requires ext-bcmath * -> the requested PHP extension bcmath is missing from your system.
    - php-amqplib/php-amqplib v2.6.0 requires ext-bcmath * -> the requested PHP extension bcmath is missing from your system.
    - Installation request for php-amqplib/php-amqplib 2.6.* -> satisfiable by php-amqplib/php-amqplib[v2.6.0, v2.6.1, v2.6.2, v2.6.3].

  To enable extensions, verify that they are enabled in those .ini files:
    - /etc/php.ini
    - /etc/php.d/20-bz2.ini
    - /etc/php.d/20-calendar.ini
    - /etc/php.d/20-ctype.ini
...
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.

if you look in the console for all extensions, you see this

...
Additional .ini files parsed:  /etc/php.d/20-bcmath.ini,
...

Not sure why gitlab-runner doesn't want to see this extension?