fmf: Use different heuristic for number of process with many CPUs

Downstream we sometimes end up with machines with lots of CPUs which
leads to running out of memory when trying to run the tests in VMs.
So let's switch to a different heuristic when we have lots of CPUs to
avoid running out of memory.

test/fmf/integration-tests/test.sh

@@ -100,6 +100,13 @@ if [[ ! -e /dev/kvm ]]; then
     export TEST_NO_QEMU=1
 fi
 
+NPROC=$(nproc)
+if [[ $NPROC -ge 10 ]]; then
+    NPROC=$((NPROC / 2))
+else
+    NPROC=$((NPROC - 1))
+fi
+
 # Create missing mountpoint for mkosi sandbox.
 mkdir -p /etc/pacman.d/gnupg
 
@@ -115,6 +122,6 @@ mkosi -f sandbox \
     --suite integration-tests \
     --print-errorlogs \
     --no-stdsplit \
-    --num-processes "$(($(nproc) - 1))"
+    --num-processes "$NPROC"
 
 popd