Add LD_PRELOAD for Coupled Model

[mathomp4]

Recent testing with mom5 by @yvikhlya and @sanAkel (see GEOS-ESM/GEOSgcm#352 and GEOS-ESM/GEOSgcm#430) in GEOSgcm has shown a need to bring back the old LD_PRELOAD mechanism that was removed in #204. So this PR brings back LD_PRELOAD but only in the case of MOM5

Obviously not ideal, but until this oddity can be examined by @tclune and @weiyuan-jiang (and maybe @atrayano), we bring back LD_PRELOAD ONLY when running MOM5 as runs of MOM6 don't seem to care!

As @yvikhlya pointed out below, MOM6 might only work due to luck. So we preload both.

[yvikhlya]

@mathomp4 I thinks both MOM5 and MOM6 need explicit LD_PRELOAD. MOM6 does not care now because it luckily goes first in load list (check ldd GEOSgcm.x), but if somebody will change something in cmake for example which will cause libmom6.so to go behind libmom5.so, we will scratch our heads again, why MOM6 does not work

[mathomp4]

@mathomp4 I thinks both MOM5 and MOM6 need explicit LD_PRELOAD. MOM6 does not care now because it luckily goes first in load list (check ldd GEOSgcm.x), but if somebody will change something in cmake for example which will cause libmom6.so to go behind libmom5.so, we will scratch our heads again, why MOM6 does not work

Hmm. Well, I can add that if you like. Give me a second...

[mathomp4]

@yvikhlya Okay, this should now preload both.

[mathomp4]

Note: I probably need to generalize this for macOS since it is libmom6.dylib on that. I'll need to figure the best way to do this.

[mathomp4]

I've pushed my generalized updates. Honestly, I think LD_PRELOAD might be ignored on macOS, not sure as it seemed to work with both .so and .dylib and the first obviously doesn't exist. But, well, I figure we should at least make it look right on macOS. 😄

[sanAkel]

Seems to work for MOM6.

I have no working restarts at 1-deg for MOM5, but by the history of this issue and given the lines of changes, I am confident that it will work for MOM5 as well.

For the record, this PR
fixes: GEOS-ESM/GEOSgcm#430
and
resolves: GEOS-ESM/GEOSgcm#352