Add memory error handler when requested via the

[schveiguy]

DMD_INSTALL_MEMERR_HANDLER=1 environment variable. Only works on DMD,
and currently only on Linux.

See #11574 for more details.

I did not test the NoMain version, but I assume this should work since it should be compiled with the -main option.

[dlang-bot]

Thanks for your pull request, @schveiguy!

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Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#11646"

[schveiguy]

ping @wilzbach @MoonlightSentinel

[wilzbach]

Force-merging as auto-tester Windows machines have issues atm.

[MoonlightSentinel]

Printing this error message would require us to guess if the MEH is available for each CI machine (because it would break the TEST_OUTPUT validation).

This could be disabled via another env. variable but simply removing it should be acceptable as well.

[schveiguy]

I'm not sure if we will be always enable this feature for all CI? I mean, I have definitely seen problems with this in some cases that made the code worse than not having it installed.

In which case, it's useful for using the CI to find issues (like the original #11574), or to use it locally when a segfault happens.

Perhaps I can change the code to configure the printout based on the value of the string? Like if the environment variable is not blank, then enable the memory handler, and if the value is not "NOPRINT", then print out the message?

[MoonlightSentinel]

It doesn't need to be enabled for all CI's. I thought we could e.g. enable it e.g. for the -debug builds done on Circle and Azure* (unless it causes errors, etc).

Perhaps I can change the code to configure the printout based on the value of the string? Like if the environment variable is not blank, then enable the memory handler, and if the value is not "NOPRINT", then print out the message?

Something like that, allthough it could simply use 1 for the current behaviour and 2 for silent mode (I doubt that the silent mode is ever relevant outside of our CI's)