Double-compilation of mod_rtma_regrid.F90 causes problems for parallel build

[AlexanderRichert-NOAA]

Description

In rtma_esg_conversion.fd/CMakeLists.txt, mod_rtma_regrid.F90 is built by both the rtma_regrid_rll2esg.exe and rtma_regrid_esg2rll.exe targets. This fails intermittently on parallel builds (it happens more than 50% of attempted builds with make -j12), because two make tasks are building/working with the .mod file at the same time. This can be fixed either by making one executable a dependency of the other so they are guaranteed to build sequentially, or by creating a separate target to build the .mod file, and make both executables dependent on it. The former is probably easier.

Steps to Reproduce

Build with make -j12