ahat: build ahat-test-dump correctly with javac

Use BUILD_JAVA_LIBRARY instead of BUILD_HOST_DALVIK_JAVA_LIBRARY for
ahat-test-dump.jar so that no special handling is needed to enable
proguard obfuscation. This way the ahat-test-dump can be obfuscated
when compiled with javac as well as jack.

Bug: 64594350
Test: m ahat-test, built from scratch
Change-Id: Iad2890b314982b08da876595c3a093cd8ec9f7da