AAPT2: Fix compiler error in 32-bit host test

We now default host native tests to build both 32-bit and 64-bit
versions.

The 32-bit version of libaapt2_test was broken because it was comparing
an unsigned int to the result from std::count(std::vector), which is a
signed int. The 64-bit version compiled fine, since
std::count(std::vector) returns a long.

Change-Id: I786fcd8a54d9f78b76b19ef82ab8dda6f5c42197