The NAG Fortran compiler's `-mdir` flag sets the module output
directory but does not add the directory to the search path for using
modules. This is inconsistent with other compilers like the GNU Fortran
compiler's `-J` flag that does both. In order to make these consistent,
add the module output directory with a `-I` flag on the NAG Fortran
compiler so that it will be searched when using modules too.
We already do this for the XL Fortran compiler since commit 210b0b99a9
(XL: Fix using Fortran modules from their output directory, 2020-02-28,
v3.18.0-rc1~640^2~1).
The Numerical Algorithms Group (NAG) Fortran compiler documents -PIC for
position-independent code and does not have a separate option for PIE.
We added `-PIC` for PIC in commit v2.8.11~174^2 (NAG: Use -PIC for
Fortran position-independent code, 2013-02-18). Follow up for PIE.
Closes: #16236
Define a "Fortran_FORMAT" target and source file property. Initialize
the target property from a "CMAKE_Fortran_FORMAT" variable. Interpret
values "FIXED" and "FREE" to indicate the source file format. Append
corresponding flags to the compiler command line.
On Linux the NAG Fortran compiler uses gcc under the hood to link. Use
"-Wl,-v" to pass "-v" to the underlying gcc compiler to get verbose link
output. Detect the NAG Fortran directory (using -dryrun) and then honor
object files in the directory referenced in the implicit link line.
Pass real linker options with "-Wl,-Xlinker,". The -Wl, gets through
the NAG front-end and the -Xlinker gets through the gcc front-end.
