fftw: PGI compiler has trouble with avx2/avx-512 SIMD support  (#20546)
fftw: PGI compiler has trouble with avx2/avx-512 SIMD support  (#20546)

* PGI compiler has trouble with avx2 SIMD support
(https://github.com/FFTW/fftw3/issues/78)

* Hew to the project's preferred indentation standard.

* Expand '%nvhpc' logic to include '%pgi'.

* Exceeded the max line-length.

* Break up the long compound statement into nested if's.

* Inadvertently picked up an extraneous file.

* PGI compiler has trouble with avx2/avx-512 SIMD support, too.
LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack