Mark the module as VNDK or VNDK-SP in Android.bp

As a VNDK/VNDK-SP module, Android.bp must have 'vndk' tag as well
as 'vendor_available: true'.

For a VNDK module, the 'vndk' tag has 'enabled: true'.
It will be installed system/lib(64)/vndk as a vendor variant.

For a VNDK-SP module, the 'vndk' tag has
'support_system_process: true' as well as 'enabled: true'.
It will be installed system/lib(64)/vndk-sp as a vendor variant.

Bug: 63866913
Test: build and boot with BOARD_VNDK_VERSION=current
Change-Id: I8df3b9ec1a867fdbaac8cf348da4cfd56433435b

Android.bp

@@ -76,6 +76,10 @@ cc_library_shared {
     name: "libc++",
     host_supported: true,
     vendor_available: true,
+    vndk: {
+        enabled: true,
+        support_system_process: true,
+    },
     clang: true,
     whole_static_libs: ["libc++_static"],
     stl: "none",