Fix a compiling issue (#526) (#527)

* Python.h not found when compiling acs_py_enclave.c

Signed-off-by: Gordon <garyw@apache.org>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 95dc495..94b9aff 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -217,7 +217,7 @@
 set_target_properties(pycomponent PROPERTIES ARCHIVE_OUTPUT_DIRECTORY
                                              ${TEACLAVE_OUT_DIR})
 target_compile_definitions(pycomponent PUBLIC SGX)
-if(NOT EXISTS "/usr/lib/pypy/include")
+if(NOT EXISTS "/usr/lib/pypy/include/Python.h")
   message(
     FATAL_ERROR
       "pypy development package not found\nFor Ubuntu, please run `apt-get install pypy-dev`"