Draft: nvhpc compiler support on grace CPU

Start adding support for nvhpc compiler with SWIFT on grace ARM CPU.

Mostly a guess but it compiles using the nvc compiler on COSMA using configure:

./configure --disable-mpi --disable-hand-vec --enable-compiler-warnings=yes

and a set of packages built with the system GCC compiler.

Still some compiler warnings to worry about, so need to poison compiler warnings, but adding dummy size to the empty structs stops the compiler from crashing.

Testing shows a performance gap from this compiler to both LLVM and GCC and the changes needed seem intrusive, so this should not be merged into the main branch unless that changes. Developers may want to keep this up to date wrt to master.

Having said that some changes here support GCC on grace, so should be extracted into another MR.