Add _testinternalcapi to OBJECT_DIRS

Author: zanieb

cpython-unix/build-cpython.sh

@@ -843,7 +843,7 @@ ${BUILD_PYTHON} ${ROOT}/fix_shebangs.py ${ROOT}/out/python/install
 # downstream consumers.
 OBJECT_DIRS="Objects Parser Parser/pegen Programs Python"
 OBJECT_DIRS="${OBJECT_DIRS} Modules"
-for ext in _blake2 cjkcodecs _ctypes _ctypes/darwin _decimal _expat _hacl _io _multiprocessing _sha3 _sqlite _sre _xxtestfuzz ; do
+for ext in _blake2 cjkcodecs _ctypes _ctypes/darwin _decimal _expat _hacl _io _multiprocessing _sha3 _sqlite _sre _testinternalcapi _xxtestfuzz ; do
     OBJECT_DIRS="${OBJECT_DIRS} Modules/${ext}"
 done