Bug 1619985: use a unique package platform for aarch64 windows builds r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D66278

--HG--
extra : moz-landing-system : lando

toolkit/mozapps/installer/package-name.mk

@@ -26,9 +26,13 @@ ifeq ($(OS_ARCH),WINNT)
 ifeq ($(CPU_ARCH),x86)
 MOZ_PKG_PLATFORM := win32
 else
+ifeq ($(CPU_ARCH),aarch64)
+MOZ_PKG_PLATFORM := win64-aarch64
+else
 MOZ_PKG_PLATFORM := win64
 endif
 endif
+endif
 ifeq ($(OS_ARCH),Darwin)
 MOZ_PKG_PLATFORM := mac
 endif