pyoxidizer: don't use in-memory for resources on macOS

When trying to debug something else on macOS, pyoxidized builds were failing
with the following message about pywatchman (and then cext.base85 when I
commented out pywatchman):

    "cannot be loaded from memory but memory loading required"

I don't have any immediate plans to do more work on macOS, but maybe this will
save someone else time debugging this.

Differential Revision: https://phab.mercurial-scm.org/D11451

rust/hgcli/pyoxidizer.bzl

@@ -33,6 +33,7 b' SIGNING_SUBJECT_NAME = VARS.get("SIGNING'
 TIME_STAMP_SERVER_URL = VARS.get("TIME_STAMP_SERVER_URL", "http://timestamp.digicert.com")
 
 IS_WINDOWS = "windows" in BUILD_TARGET_TRIPLE
+IS_MACOS = "darwin" in BUILD_TARGET_TRIPLE
 
 # Code to run in Python interpreter.
 RUN_CODE = """
@@ -69,7 +70,7 b' def make_distribution():'
     return default_python_distribution(python_version = "3.9")
 
 def resource_callback(policy, resource):
-    if not IS_WINDOWS:
+    if not (IS_WINDOWS or IS_MACOS):
         resource.add_location = "in-memory"
         return
 
@@ -100,7 +101,7 b' def make_exe(dist):'
     # extensions.
     packaging_policy.extension_module_filter = "all"
     packaging_policy.resources_location = "in-memory"
-    if IS_WINDOWS:
+    if IS_WINDOWS or IS_MACOS:
         packaging_policy.resources_location_fallback = "filesystem-relative:lib"
     packaging_policy.register_resource_callback(resource_callback)