Allow to set `panic='abort'` in `build-override`

[link2xt]

Problem

Currently trying to create a section [profile.dev.build-override] with panic='abort' results in error "panic may not be specified in a build-override profile".

This validation seems to have been added for the test override to make sure tests are not built without panic='unwind' according to discussions in #5384 (comment)

Proposed Solution

Remove unnecessary validation for the build override.

Notes

This issue is a spin-off of #12645

[ehuss]

It is not possible to build proc-macros with abort since they are loaded within the compiler. Additionally, some build scripts will fail with panic=abort since they rely on catching unwinding. Can you say more about what you are trying to do and why?

[link2xt]

I am building my dependencies with panic='abort' to save space and wanted to avoid building the same dependency another time as a build dependency: #12645

[weihanglo]

It's unfortunate there are some limitations described in #12647 (comment). I would probably unset panic=abort in dev profile if appropriate, and only set it in release profile.

Closing. If you have an idea to circumvent the behavior, please share.

See also #12645 (comment)