`lfric_atm` crashes when compiling with Genoa craylibs

### Version

main

### Are there any linked Issues or Pull Requests?

#621

### What happened?

Internal compiler error when trying to compile `lfric_atm` using `craype-x86-genoa` and `mo-craylibs-genoa/1.0` at optimisation level "production". This can be avoided by changing the compiler flags for the `melt_ctl` to use `-O0`.

### Relevant log output

```shell
ftn-7991 ftn: INTERNAL MELT_CTL, File = convection/comorph/moist_proc/melt_ctl.F90, Line = 280
INTERNAL COMPILER ERROR: "arithmetic or typeless types expected" (/home/jenkins/crayftn/pdgcs/v_expr_utl.c, line 9095,
```

Start with convection/comorph/moist_proc/melt_ctl.F90 around line 280 and reproduce the production build using craype-x86-genoa with mo-craylibs-genoa/1.0. Compare the failing optimization settings with the reported -O0 workaround, and review linked issue #621 for context. Done should mean lfric_atm compiles without the reported internal compiler error under the intended production settings.

Written by the indexing model from the issue text.