Add Om1 lowering with no optimizations

crosstest/simple_loop.c

Index: crosstest/simple_loop.c
diff --git a/crosstest/simple_loop.c b/crosstest/simple_loop.c
new file mode 100644
index 0000000000000000000000000000000000000000..6568380de318f72fba9cd721dee631ffe079e50c
--- /dev/null
+++ b/crosstest/simple_loop.c
@@ -0,0 +1,10 @@
+// This is a simple loop that sums elements of an input array and
+// returns the result.  It's here mainly because it's one of the
+// simple examples guiding the early Subzero design.
+
+int simple_loop(int *a, int n) {
+  int sum = 0;
+  for (int i = 0; i < n; ++i)
+    sum += a[i];
+  return sum;
+}