Move hipfort library to a compiler-specific subdirectory

[cgmb]

Motivation

Change the hipfort install directory layout to prevent fortran compilers from linking against a copy of the hipfort library that has been built with a different compiler. This adopts the convention proposed by Alistair McKinstry for the Debian project for supporting multiple fortran toolchains side-by-side in the same FHS root. The scope of this PR, however, is limited to the archive file. To fully adopt the Debian convention, the mod files would also have to move.

Technical Details

This change updates the default installation LIBDIR to include the compiler name.

Test Plan

It should be verified that the hipfort library is found in "/opt/rocm-7.0.1/lib/fortran/amdflang/libhipfort-amdgcn.a" after installing the hipfort package, and that libraries using find_package(hipfort) and linking against targets such as hipfort::hip continue to build and link correctly.

Test Result

Todo.