Consider lowering minimum clang version to 16 for bioconda compatibility

[corneliusroemer]

Bioconda currently uses clang 16 for osx which might make it difficult to add iqtree with cmaple feature flag to bioconda.

Would it be possible to lower the minimum version requirement to 16, from 17?

See my attempts over at bioconda-recipe here:

• https://github.com/bioconda/bioconda-recipes/pull/49360

[corneliusroemer]

Seems like this wasn't an issue - could compile with clang 16 without problems.