Switch aarch64 toolchain components to overlay convention

.orchestra/config/components.yml

 #@ load("@ytt:template", "template")
 #@ load("@ytt:data", "data")
 
-#@ load("/components/toolchain/arch/aarch64.lib.yml", "aarch64_toolchain_components")
 #@ load("/components/toolchain/arch/s390x.lib.yml", "s390x_toolchain_components")
 #@ load("/components/toolchain/arch/mips.lib.yml", "mips_toolchain_components")
 #@ load("/components/toolchain/arch/mipsel.lib.yml", "mipsel_toolchain_components")
@@ -12,7 +11,6 @@
 
 #@ load("/global_options.lib.yml", "options")
 components:
-  _: #@ template.replace(aarch64_toolchain_components)
   _: #@ template.replace(s390x_toolchain_components)
   _: #@ template.replace(mips_toolchain_components)
   _: #@ template.replace(mipsel_toolchain_components)

.orchestra/config/components/toolchain/arch/aarch64.lib.yml → .orchestra/config/components/toolchain/arch/aarch64.yml

+#@ load("@ytt:overlay", "overlay")
 #@ load("/components/toolchain/lib/toolchain.lib.yml", "create_toolchain_components")
 
 #@ def _params():
@@ -19,6 +20,7 @@ extra_gcc_configure_options:
 dynamic: "0"
 #@ end
 
+#@overlay/match by=overlay.all, expects=1
+#@overlay/match-child-defaults missing_ok=True
 ---
-
-#@ aarch64_toolchain_components = create_toolchain_components(**_params())
+components: #@ create_toolchain_components(**_params())