The previously-used `-Werror all-warnings` is not supported by
the NVHPC suite of compilers. This previously worked since `-Werror`
was being used and `all-warnings` was being excluded.
We thought this was the correct syntax due to incorrect documentation
about `-Werror`, which stated the argument should be space-separated,
while it should actually be separated with `=` or `,`.
Issue: #24665
In commit 76a08cd253 (COMPILE_WARNING_AS_ERROR: Add options to treat
warnings as errors, 2022-04-21, v3.24.0-rc1~173^2) we formatted the
options table entries as command-line string fragments. Since they are
part of the `CMAKE_${lang}_COMPILE_OPTIONS_*` tables, they should be
formatted as `;`-separated lists of compiler options.
Add `COMPILE_WARNING_AS_ERROR` target property and supporting
`CMAKE_COMPILE_WARNING_AS_ERROR` variable.
`COMPILE_WARNING_AS_ERROR` is initialized by
`CMAKE_COMPILE_WARNING_AS_ERROR`. It is a boolean variable. If it is
true, it expands to a different flag depending on the compiler such that
any warnings at compile will be treated as errors.
Supports compiler ids that I could find a relevant flag for.
Identify the compilers as `NVHPC` to distinguish it from the older PGI
compilers from which they evolved, and from other `NVIDIA` compilers.
Fixes: #20887
