Keep py-next/step working in gdb script even when in native code

Summary: When I was testing this I only ever interrupted code directly in the interperter loop. It turns out that if we're in native code (called from the interpreter) we need to manually crank the handle a bit to get to a valid Python frame.

Reviewed By: alexmalyshev

Differential Revision: D57707850

fbshipit-source-id: a9990e0833240053c7fbddf223fa5b1ce369618e

Tools/gdb/libpython.py

@@ -2042,11 +2042,18 @@ def invoke(self, args, from_tty):
         global _PyRunningTargetFrameBackAddress
 
         frame = Frame.get_selected_python_frame()
+        # Aparently this frame is not actually a Python frame, so we need to
+        # walk to find it. This is based on the implementation around the 
+        # PyUp/PyDown commands.
+        while frame:
+            if frame.is_python_frame():
+                pyop_frame = frame.get_pyop()
+                if pyop_frame:
+                    break
+            frame = frame.older()
         if not frame:
             print('Unable to locate python frame')
             return
-
-        pyop_frame = frame.get_pyop()
         if not pyop_frame:
             print(UNABLE_READ_INFO_PYTHON_FRAME)
             return
@@ -2066,4 +2073,3 @@ def invoke(self, args, from_tty):
 #     gdb.execute('call (void*)dlopen("gdb_dbg.cpython-312-x86_64-linux-gnu.so", 2)')
 
 # PyRunningInit()
-