Suggested enhancement

Hello, I'm maintaining the MbedTLS package on the Gentoo Linux system. We have multiple packages that still depend on MbedTLS 2, so in order to build them we need 2.* branches installed. Unfortunately, there are also a number of packages that already require newer version 3.*.
We need to enhance the CMake buildsystem in a way that will allow us to have both 2 and 3 versions. By default, 2 and 3 cannot be installed simultaneously due path conflicts in lib and include directories.

Justification

Mbed TLS needs this because many packages still stick or are unable to migrate to 3 versions. We need a way to install both versions and let packages decide what to choose between them.

See also https://bugs.gentoo.org/805011 for actual problem and rationale.