Ignore python env vars which might load incompatible libs. Refs #902

* PYTHONHOME is used *ahead* of the python36.zip on Python's default
  search path, so we need to suppress that to make sure it doesn't
  interfere.

qrenderdoc/Code/pyrenderdoc/PythonContext.cpp

@@ -221,6 +221,8 @@ void PythonContext::GlobalInit()
 
   Py_SetProgramName(program_name);
 
+  Py_IgnoreEnvironmentFlag = 1;
+
   Py_Initialize();
 
   PyEval_InitThreads();