Update Marl to 64d123947

A single change to fix windows breakage due to 'alloc' requiring an underscore prefix on some toolchains.

Changes:
    64d123947 thread.cpp: Replace use of alloca with vector.

Commands:
    git subtree pull --prefix third_party/marl https://github.com/google/marl master --squash

Bug: b/140546382
Bug: angleproject:4474
Change-Id: If15baa2531a5b49537bb0ba9f190454f2044ad9b
diff --git a/third_party/marl/src/thread.cpp b/third_party/marl/src/thread.cpp
index fa69bdf..afb4432 100644
--- a/third_party/marl/src/thread.cpp
+++ b/third_party/marl/src/thread.cpp
@@ -124,8 +124,9 @@
   MARL_ASSERT(size > 0,
               "InitializeProcThreadAttributeList() did not give a size");
 
+  std::vector<uint8_t> buffer(size);
   LPPROC_THREAD_ATTRIBUTE_LIST attributes =
-      reinterpret_cast<LPPROC_THREAD_ATTRIBUTE_LIST>(alloca(size));
+      reinterpret_cast<LPPROC_THREAD_ATTRIBUTE_LIST>(buffer.data());
   CHECK_WIN32(InitializeProcThreadAttributeList(attributes, 1, 0, &size));
   defer(DeleteProcThreadAttributeList(attributes));