Allow finding tblite as dependency

[awvwgk]

• has to find mctc-lib explicitly, since modules are used src/tblite.f90
• make sure we can link statically against external dependencies

[awvwgk]

@JayTheDog You can give it a try on majestix with

git clone https://github.com/awvwgk/QCxMS && cd QCxMS
git checkout dependency
module load intel tblite
meson setup _build --default-library=static --buildtype=release -Dfortran_link_args="-qopenmp -static" -Dfortran_args="-Ofast -axAVX2 -mtune=core-avx2 -fma"

This should greatly reduce build time and also use the specially tuned version of tblite I compiled for our micro archs.