Build pybindings with -D_GLIBCXX_USE_CXX11_ABI=0 to match libtorch.so

libtorch.so builds with the old glibc ABI, so we need to as well,
for any source files that include torch headers.

CMakeLists.txt

@@ -526,7 +526,11 @@ if(EXECUTORCH_BUILD_PYBIND)
   # compile options for pybind
 
   set(_pybind_compile_options -Wno-deprecated-declarations -fPIC -frtti
-                              -fexceptions)
+                              -fexceptions
+                              # libtorch is built with the old ABI, so we need
+                              # to do the same for any .cpp files that include
+                              # torch, c10, or ATen targets.
+                              -D_GLIBCXX_USE_CXX11_ABI=0)
   # util lib
   add_library(
     util