tests/aiger: Compare .aag outputs against known

Any files that differ (e.g. due to compiler order of operations changing) will trigger an error.

tests/aiger/.gitignore

@@ -1,2 +1,3 @@
 /*_ref.v
 /neg.out/
+/gate/

tests/aiger/run-test.sh

@@ -57,3 +57,9 @@ for y in *.ys; do
     echo "Running $y."
     ../../yosys -ql ${y%.*}.log $y
 done
+
+# compare aigmap with reference
+# make gold with: rm gold/*; yosys --no-version -p "test_cell -aigmap -w gold/ -n 1 -s 1 all"
+rm -rf gate; mkdir gate
+../../yosys --no-version -p "test_cell -aigmap -w gate/ -n 1 -s 1 all"
+diff --brief gold gate | tee aigmap.err