Occlusion culling fixes

Fixes some issues found by UBSAN and other misc things:
* Fixed memory leak on exit.
* Properly align ray packet buffer to 64 bytes.
* Added some compiler flags from Embree's build system.
* Fixed ray masks.

modules/raycast/SCsub

@@ -86,6 +86,20 @@ if env["builtin_embree"]:
         # Embree needs those, it will automatically use SSE2NEON in ARM
         env_thirdparty.Append(CPPDEFINES=["__SSE2__", "__SSE__"])
 
+    if not env.msvc:
+        env_thirdparty.Append(
+            CPPFLAGS=[
+                "-fno-strict-overflow",
+                "-fno-delete-null-pointer-checks",
+                "-fwrapv",
+                "-fsigned-char",
+                "-fno-strict-aliasing",
+                "-fno-tree-vectorize",
+                "-fvisibility=hidden",
+                "-fvisibility-inlines-hidden",
+            ]
+        )
+
     env.modules_sources += thirdparty_obj