_variables: Cythonize _internal_expand

Move _variables.py to be a Cython module.

`_internal_expand` is a function that is called a lot in BuildStream.
It is also entirely isolated and easy to cythonize.

1 files changed, 1 insertions, 0 deletions

diff --git a/setup.py b/setup.py
index fe977c123..90aa74d31 100755
--- a/setup.py
+++ b/setup.py
@@ -391,6 +391,7 @@ def register_cython_module(module_name, dependencies=None):
 
 BUILD_EXTENSIONS = []
 
+register_cython_module("buildstream._variables")
 
 #####################################################
 #             Main setup() Invocation               #