Workaround for multiprocessing shared memory limits

This affects musl libc and macos, see:
sagemath#36741 (comment)

We are working on a better fix to avoid using multiprocessing in
sage.features, but this will do meanwhile.

There is agreement that disabling the lock is completely harmless, since
the counter is not really used for anything; disabling the lock fixes
the issues that we had on 10.4.beta0.

src/sage/features/__init__.py

@@ -162,7 +162,7 @@ def __init__(self, name, spkg=None, url=None, description=None, type='optional')
         # shared among subprocesses. Thus we use the Value class from the
         # multiprocessing module (cf. self._seen of class AvailableSoftware)
         from multiprocessing import Value
-        self._num_hidings = Value('i', 0)
+        self._num_hidings = Value('i', 0, lock=False)
 
         try:
             from sage.misc.package import spkg_type