Reproduce crash when including system headers

The following
    $ ./includegraph.py examples/example1/build/ -l DEBUG
    2022-04-15 11:42:46,871 - ./includegraph.py - DEBUG - Successfully loaded compilation database from build directory 'examples/example1/build/'
    2022-04-15 11:42:46,872 - ./includegraph.py - DEBUG - Getting headers for /home/nots/Documents/includegraph/examples/example1/src/example1.cpp
    /../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/istream
        /../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/istream.tcc

Crashes in clang.cindex.File.name, which calls clang_getFileName() from
the cdll loaded libclang.so

    #0  0x00007f21db0106ba in clang_getFileName () from /home/nots/Documents/includegraph/.venv/lib/python3.8/site-packages/clang/native/libclang.so
    #1  0x00007f21de1ecff5 in ?? () from /lib/x86_64-linux-gnu/libffi.so.7
    #2  0x00007f21de1ec40a in ?? () from /lib/x86_64-linux-gnu/libffi.so.7
    #3  0x00007f21dd752306 in _ctypes_callproc () from /usr/lib/python3.8/lib-dynload/_ctypes.cpython-38-x86_64-linux-gnu.so

It _doesn't_ crash if you comment out the File.name accesses, but if you
do this, then it breaks the graph generation.

examples/example1/src/circular.h

@@ -1,2 +1,3 @@
 #pragma once
 #include "private.h"
+#include <string>

examples/example1/src/example1.cpp

@@ -1,3 +1,4 @@
 #include <example1/foo.h>
 #include <example1/bar.h>
 #include "private.h"
+#include <iostream>

examples/example1/src/private.h

@@ -1,2 +1,3 @@
 #pragma once
 #include "circular.h"
+#include <vector>

includegraph.py

@@ -128,9 +128,9 @@ def build_header_dependency_graph(includes: Iterable[FileInclusion]) -> Dict:
     graph = collections.defaultdict(list)
     file_include: FileInclusion
     for file_include in includes:
-        logging.debug("Found header inclusion: %s", file_include)
-        source = file_include.source.name
-        included_file = file_include.include.name
+        # logging.debug("Found header inclusion: %s -> %s", file_include.source, file_include.include)
+        source = file_include.source#.name
+        included_file = file_include.include#.name
         graph[source].append(included_file)
 
     return graph