Mono.Android-Tests and Xamarin.Forms-Performance-Integration should build against system instalation

[radekdoulik]

The #2153 added dependency on _CreateJavaInteropDllConfigs target, which only works inside the XA build.

I should make the target conditional, so that these tests are still possible to build outside of XA source tree.

[pjcollins]

This was also discussed in #2683.

Should be resolved in:
#3042
and
#3235