build: incl "frozenlist" dep as pure-python, without C stuff

While attempting to reproducibly build the qml android apk, one of the differences
was due to the "frozenlist" dependency (pulled in by aiohttp) - the compiled C parts
were not deterministic. By setting this env var, we can opt-out [0] of all the C
accelerated parts and just use the pure-python implementation. We are already doing
the same for other aiohttp-related packages anyway.

[0]: c2794cac12/setup.py (L7)

contrib/make_packages

@@ -29,6 +29,7 @@ python -m pip install --no-build-isolation --no-dependencies --no-warn-script-lo
 export AIOHTTP_NO_EXTENSIONS=1
 export YARL_NO_EXTENSIONS=1
 export MULTIDICT_NO_EXTENSIONS=1
+export FROZENLIST_NO_EXTENSIONS=1
 
 # if we end up having to compile something, at least give reproducibility a fighting chance
 export LC_ALL=C