DLL Suffix Panic

[not-matthias]

Problem

When changing the dll suffix an assertion will be triggered. I'm using cargo-xbuild to build a custom target and there I can add an option to change the suffix.

Steps

I created a repository with an example and the steps how to reproduce it: https://github.com/not-matthias/rust-dll-extension

Possible Solution(s)
Only the dll suffix has been changed and the dll is still the same. Thus it should be possible to just remove the assertion.

Here's the affected code:

• https://github.com/rust-lang/cargo/blob/master/src/cargo/core/compiler/build_context/target_info.rs#L303
• https://github.com/rust-lang/cargo/blob/master/src/cargo/core/compiler/build_context/target_info.rs#L322

And here's the pull request that introduced this behaviour: #8210

Notes

OS: Windows 10

Output of cargo version:

cargo 1.45.0-nightly (9fcb8c1d2 2020-05-25)

Output of rustup show:

nightly-x86_64-pc-windows-msvc (default)
rustc 1.45.0-nightly (ad4bc3323 2020-06-01)