Disable pybind11's GIL checks (#325)

Summary:
pybind11 recently added a feature to assert that the GIL is held during reference counting operations pybind/pybind11#4246

This feature has already uncovered several instances of undefined behavior in several Python extensions.

However, this code does not seem to pass these checks, which is preventing us from upgrading PyTorch to the latest pybind11. See pytorch/pytorch#105245

This PR disables those checks, which will in turn allow PyTorch to upgrade.

Note that this code already has known potential GIL issues:

https://github.com/pytorch/multipy/blob/bd1c76f294335695db8bfa66250781c1627f4eb7/multipy/runtime/deploy.cpp#L59

Pull Request resolved: #325

Reviewed By: PaliC

Differential Revision: D47518187

Pulled By: albanD

fbshipit-source-id: 5bf14d3633afe67fe0aa8fd74610403e0c494ea5

multipy/runtime/CMakeLists.txt

@@ -9,6 +9,14 @@ project(MultipyRuntime)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+# multipy currently does not pass pybind11's GIL checks.
+#
+# This usually indicates undefined behavior or bugs within extensions, but we don't have the resources to debug
+# this package right now.
+#
+# In the future, someone should find out why this code fails to work when these checks are enabled.
+add_definitions(-DPYBIND11_NO_ASSERT_GIL_HELD_INCREF_DECREF)
+
 
 # set ABI by default to 0