Test using vectorized flags in RRTMGP

[mathomp4]

In #5 it was noted by me that in our CMakeLists.txt for RRTMGP we have:

# Use of the GEOS Vectorized flags in RRTMGP caused a segfault leading to
# line 726 of mo_gas_optics_kernels.F90. Moving to the "old" no-vect flags
# allows RRTMGP to run again.
if (CMAKE_Fortran_COMPILER_ID MATCHES Intel AND CMAKE_BUILD_TYPE MATCHES Release)
  set (CMAKE_Fortran_FLAGS_RELEASE "${GEOS_Fortran_FLAGS_NOVECT}")
endif ()

That is 2 years old so v1.5 time. We've long since moved to v1.6 and our vect flags have changed as well. So maybe this not needed anymore!

Let's do some tests:

• v1.6 → Nope! Slower with Vect Flags (see below)
• v1.7

[mathomp4]

Welp, maybe we don't want to use our vectorized flags with v1.6 based RRTMGP:

Resolution	NoVect SW	Vect SW	Speedup	NoVect LW	Vect LW	Speedup	Total NoVect	Total Vect	Speedup
c24	2.76	3.02	-9%	2.10	1.89	10%	4.86	4.91	-1%
c48	7.81	8.42	-8%	6.96	6.32	9%	14.77	14.74	0%
c90	37.56	40.14	-7%	35.34	30.36	14%	72.90	70.50	3%
c180	51.66	58.20	-13%	51.22	48.69	5%	102.88	106.89	-4%
c360	52.75	61.24	-16%	52.26	49.35	6%	105.01	110.59	-5%
c720	56.89	81.42	-43%	53.47	50.51	6%	110.36	131.93	-20%

[mathomp4]

So that is not good for v1.6 but RRTMGP v1.7 is a different beast.

Note that @peterukk has an issue at the mothership (see earth-system-radiation#215) which also involves vectorization and there is no associated PR, so this still might be an issue.

I'll test with RRTMGP v1.7 when @dr0cloud has finished his integration of it into GEOS. (Reminder: also do SP v DP tests.)