Adds TIME macro to .testing/Makefile (#1230)

This simply provides a means to avoid out-of-order output when running
`make test -j` in parallel. By default we can get output like this:

```
PASS: Diagnostics tc4.dim.q.diag agree.
PASS: Diagnostics tc4.openmp.diag agree.
PASS: Diagnostics tc4.dim.r.diag agree.

real	0m16.012s
user	0m0.129s
sys	0m0.268s

real	0m15.761s
user	0m0.116s
sys	0m0.318s

real	0m15.940s
user	0m0.112s
sys	0m0.302s

real	0m15.705s
user	0m0.177s
sys	0m0.251s
DONE: tc2.a.dim.l; no runtime errors.
DONE: tc2.a.nan; no runtime errors.
DONE: tc2.dim.z; no runtime errors.
```

but by adding `TIME =` to config.mk or invoking in bash
with `TIME="" make test -j` the times are omitted and
output cleaner.

Co-authored-by: Marshall Ward <marshall.ward@noaa.gov>

.testing/Makefile

@@ -27,6 +27,8 @@ FCFLAGS_COVERAGE ?=
 # Set to `true` to require identical results from DEBUG and REPRO builds
 DO_REPRO_TESTS ?=
 
+TIME ?= time
+
 # Many compilers (Intel, GCC on ARM64) do not yet produce identical results
 # across DEBUG and REPRO builds (as defined below), so we disable on default.
 
@@ -188,7 +190,7 @@ build/target/configure: $(TARGET_SOURCE)
 # Build MOM6
 .PRECIOUS: $(foreach b,$(BUILDS),build/$(b)/MOM6)
 build/%/MOM6: build/%/Makefile
-	cd $(@D) && time $(MAKE) -j
+	cd $(@D) && $(TIME) $(MAKE) -j
 
 
 # Use autoconf to construct the Makefile for each target
@@ -408,7 +410,7 @@ work/%/$(1)/ocean.stats work/%/$(1)/chksum_diag: build/$(2)/MOM6 $(VENV_PATH)
 	mkdir -p $$(@D)/RESTART
 	echo -e "$(4)" > $$(@D)/MOM_override
 	cd $$(@D) \
-	  && time $(5) $(MPIRUN) -n $(6) ../../../$$< 2> std.err > std.out \
+	  && $(TIME) $(5) $(MPIRUN) -n $(6) ../../../$$< 2> std.err > std.out \
 	  || !( \
 	    mkdir -p ../../../results/$$*/ ; \
 	    cat std.out | tee ../../../results/$$*/std.$(1).out | tail -20 ; \
@@ -469,7 +471,7 @@ work/%/restart/ocean.stats: build/symmetric/MOM6 $(VENV_PATH)
 	  && halfperiod=$$(printf "%.f" $$(bc <<< "scale=10; 0.5 * $${daymax} * $${timeunit_int}")) \
 	  && printf "\n&ocean_solo_nml\n    seconds = $${halfperiod}\n/\n" >> input.nml
 	# Run the first half-period
-	cd $(@D) && time $(MPIRUN) -n 1 ../../../$< 2> std1.err > std1.out \
+	cd $(@D) && $(TIME) $(MPIRUN) -n 1 ../../../$< 2> std1.err > std1.out \
 	  || !( \
 	    cat std1.out | tee ../../../results/$*/std.restart1.out | tail ; \
 	    cat std1.err | tee ../../../results/$*/std.restart1.err | tail ; \
@@ -480,7 +482,7 @@ work/%/restart/ocean.stats: build/symmetric/MOM6 $(VENV_PATH)
 	mkdir $(@D)/RESTART
 	cd $(@D) && sed -i -e "s/input_filename *= *'n'/input_filename = 'r'/g" input.nml
 	# Run the second half-period
-	cd $(@D) && time $(MPIRUN) -n 1 ../../../$< 2> std2.err > std2.out \
+	cd $(@D) && $(TIME) $(MPIRUN) -n 1 ../../../$< 2> std2.err > std2.out \
 	  || !( \
 	    cat std2.out | tee ../../../results/$*/std.restart2.out | tail ; \
 	    cat std2.err | tee ../../../results/$*/std.restart2.err | tail ; \