Fix incorrect musl detection causing turbo to fail on some systems

[AJenbo]

The current implementation checks for musl tools being installed which can be true even if your system is glibc based... for example if you build things using musl. Instead it's better to look at what's in /proc/self/maps.

Context: On 2.2.10 I get the following error

PHP Warning: PHP Startup: Unable to load dynamic library './vendor/phpstan/phpstan/turbo-ext/linux-musl-x86_64/phpstan_turbo-8.5.so' (tried: ./vendor/phpstan/phpstan/turbo-ext/linux-musl-x86_64/phpstan_turbo-8.5.so (libc.musl-x86_64.so.1: cannot open shared object file: No such file or directory), /usr/lib/php/20250925/./vendor/phpstan/phpstan/turbo-ext/linux-musl-x86_64/phpstan_turbo-8.5.so.so (/usr/lib/php/20250925/./vendor/phpstan/phpstan/turbo-ext/linux-musl-x86_64/phpstan_turbo-8.5.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0

[staabm]

Can the initial error be reproduced in CI?

[AJenbo]

Yes you could run apt install musl-tools and then it should trigger the issue.

I'm not exactly sure if this would be worth adding a new CI job for, or if it would fit in to one of the existing ones.

[ondrejmirtes]

Added a failing test. #6311

I rebase this PR, the test should pass.

[ondrejmirtes]

Thank you!