Bug 1687783 - Part 1: Enable MOZ_UPDATE_AGENT by default on macOS and Windows. r=firefox-build-system-reviewers,mhentges

At the same time, remove the global define, which isn't necessary and
triggers some rebuilds.  Nothing is using MOZ_UPDATE_AGENT right now
so it's safe to enable more broadly, and it will be used to gate new
background update work.

Differential Revision: https://phabricator.services.mozilla.com/D102786

build/moz.configure/update-programs.configure

@@ -35,26 +35,23 @@ set_config(
     depends_if("--enable-maintenance-service", when=target_is_windows)(lambda _: True),
 )
 
-# Update agent (currently Windows only)
+# Update agent (currently Windows and macOS only)
 # This is an independent task that runs on a schedule to
 # check for, download, and install updates.
 # ==============================================================
 
 option(
-    "--enable-update-agent",
-    when=target_is_windows,
-    default=False,
+    "--disable-update-agent",
+    when=target_is_windows | target_is_osx,
+    default=True,
     help="{Enable|Disable} building update agent",
 )
 
-set_define(
-    "MOZ_UPDATE_AGENT",
-    depends_if("--enable-update-agent", when=target_is_windows)(lambda _: True),
-)
-
 set_config(
     "MOZ_UPDATE_AGENT",
-    depends_if("--enable-update-agent", when=target_is_windows)(lambda _: True),
+    depends_if("--enable-update-agent", when=target_is_windows | target_is_osx)(
+        lambda _: True
+    ),
 )
 
 # Enable or disable the default browser agent, which monitors the user's default

toolkit/components/taskscheduler/moz.build

@@ -9,18 +9,18 @@ with Files("**"):
 
 XPCSHELL_TESTS_MANIFESTS += ["tests/xpcshell/xpcshell.ini"]
 
-XPIDL_MODULE = "taskscheduler"
-XPCOM_MANIFESTS += ["components.conf"]
-
 EXTRA_JS_MODULES += ["TaskScheduler.jsm"]
 
 # This whole component is currently Windows-only, but a Mac implementation is planned.
 # Only the Windows C++ interface is an XPCOM component.
 if CONFIG["OS_TARGET"] == "WINNT":
     EXTRA_JS_MODULES += ["TaskSchedulerWinImpl.jsm"]
+    XPCOM_MANIFESTS += ["components.conf"]
+    XPIDL_MODULE = "taskscheduler"
     XPIDL_SOURCES += ["nsIWinTaskSchedulerService.idl"]
     EXPORTS += ["nsWinTaskScheduler.h"]
     SOURCES += ["nsWinTaskScheduler.cpp"]
     OS_LIBS += ["taskschd"]
+    DEFINES["UNICODE"] = True
 
 FINAL_LIBRARY = "xul"

toolkit/modules/moz.build

@@ -300,6 +300,7 @@ for var in (
     "MOZ_SYSTEM_NSS",
     "MOZ_UNSIGNED_APP_SCOPE",
     "MOZ_UNSIGNED_SYSTEM_SCOPE",
+    "MOZ_UPDATE_AGENT",
     "MOZ_UPDATER",
 ):
     if CONFIG[var]: