Upgrade slang-binaries (shader-slang#1986)

jsmall-zzz · web-flow · commit 66e319e34b99 · 2021-10-21T13:13:25.000-04:00
* #include an absolute path didn't work - because paths were taken to always be relative.

* Update slang-binaries to have centos binaries.
diff --git a/external/slang-binaries b/external/slang-binaries
@@ -1 +1 @@
-Subproject commit adebcd3226b77f4f55121fc4bf14607946527846
+Subproject commit 64dcb6b4d8e588938dbc65cb5fa30d50732486ed
