Bug 1646653 - Remove dependencies on xpcom/xpidl/export. r=froydnj

They were necessary some time ago, but:
- there is no js/xpconnect/src/export target anymore,
- accessibility/xpcom/export had a dependency on xpcom/xpidl/export for
  the ply cache files, but they're not used as of bug 1633156.
- the recursive make backend was adding automatic dependencies on
  xpcom/xpidl/export for the ply cache files.

Differential Revision: https://phabricator.services.mozilla.com/D80150

config/recurse.mk

@@ -160,10 +160,6 @@ recurse:
 	$(LOOP_OVER_DIRS)
 
 ifeq (.,$(DEPTH))
-# Interdependencies for parallel export.
-js/xpconnect/src/export: dom/bindings/export xpcom/xpidl/export
-accessible/xpcom/export: xpcom/xpidl/export
-
 # The Android SDK bindings needs to build the Java generator code
 # source code in order to write the SDK bindings.
 widget/android/bindings/export: mobile/android/base/export

python/mozbuild/mozbuild/backend/recursivemake.py

@@ -724,8 +724,6 @@ class RecursiveMakeBackend(MakeBackend):
                     if deps:
                         rule.add_dependencies(
                             '%s/%s' % (d, tier) for d in sorted(deps) if d)
-                    if dir in self._idl_dirs and tier == 'export':
-                        rule.add_dependencies(['xpcom/xpidl/%s' % tier])
             rule = root_deps_mk.create_rule(['recurse_%s' % tier])
             if main:
                 rule.add_dependencies('%s/%s' % (d, tier) for d in sorted(main))