FindHDF5: Restore parallel HDF5 detection with only CXX enabled
Since !8015 (merged), if CXX is enabled but C is
not, the _HDF5_test_regular_compiler_C
helper writes a .cpp
source
but the _HDF5_invoke_compiler
still expects a .c
source. Refactor
the logic to select a name for the source file up front, and use it in
both helpers.
Fixes: #24627 (closed)
Issue: #24241 (closed)
Backport: release