[cudnn] add other locations to find lib already installed

[cenit]

Describe the pull request

• What does your PR fix?

  Fixes [cudnn:x64-windows] build failure while installing opencv #17283
  Without this PR, CUDNN cannot be found in some default linux folders when installed with apt-get. Also, moved all reasonable variables to ENV, since CMake has to look for them, otherwise they are unuseful

• Which triplets are supported/not supported? Have you updated the CI baseline?

  all

• Does your PR follow the maintainer guide?

  Yes

• If you have added/updated a port: Have you run ./vcpkg x-add-version --all and committed the result?

  Yes

[cenit]

@rubenpraets @PBoog can you please tell me if this PR fixes your problem? It should, and it also fixes some problems I observed in some other linux configs

[rubenpraets]

I did a pull of your branch and yes, this solves my problem. Thanks!

[PBoog]

Works for me, thanks for the fix!

[BillyONeal]

Should we change this to 8 in concert with #17331 ?

[cenit]

it really depends for me
on one side, the broader the compatibility the better (and so i’d push for even a lower version in the minimum accepted by the portfile)
on another hand, these port files which are not installing anything and just finding compatible versions on the systems are already breaking binary caches at least for me. Different configs produce the same hash due to the same portfile and become invalid when consumed on the wrong system. To fix this at least reducing acceptable versions is helpful