libcutils_test: static libjsoncpp

The 32-bit variant of libjsoncpp is not always installed
on 64-bit devices, so it must always be statically included.

We should probably collapse libcutils_test with
libcutils_test_static in the future.

Bug: 285357054
Test: libcutils_test
Change-Id: Ic84901ce5af766338b2cab07c3cf10841ba9a150