test: fix x86_64-macos failures

This is just a temporary fix - I would like to unify all of x86_64
tests across linux and macos OSes.

test/incremental/x86_64-linux/assert_function.14.zig

@@ -0,0 +1,17 @@
+pub fn main() void {
+    add(aa, bb);
+}
+
+const aa = 'ぁ';
+const bb = '\x03';
+
+fn add(a: u32, b: u32) void {
+    assert(a + b == 12356);
+}
+
+pub fn assert(ok: bool) void {
+    if (!ok) unreachable; // assertion failure
+}
+
+// run
+//