tools/memory-model: Make checkghlitmus.sh use mselect7

The checkghlitmus.sh script currently uses grep to ignore non-C-language
litmus tests, which is a bit fragile.  This commit therefore enlists the
aid of "mselect7 -arch C", given Luc Maraget's recent modifications that
allow mselect7 to operate in filter mode.

This change requires herdtools 7.52-32-g1da3e0e50977 or later.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/memory-model/scripts/checkghlitmus.sh

@@ -41,7 +41,7 @@ fi
 
 # Create a list of C-language litmus tests with "Result:" commands and
 # no more than the specified number of processes.
-find litmus -name '*.litmus' -exec grep -l -m 1 "^C " {} \; > $T/list-C
+find litmus -name '*.litmus' -print | mselect7 -arch C > $T/list-C
 xargs < $T/list-C -r egrep -l '^ \* Result: (Never|Sometimes|Always|DEADLOCK)' > $T/list-C-result
 xargs < $T/list-C-result -r grep -L "^P${LKMM_PROCS}" > $T/list-C-result-short