JDK-8298448 introduced UBSan support. In later revisions of the patch I added preprocessor tests to ensure the build was correctly configured. Apparently I did not attempt to build after that. ADLC does not use any of the standard CFLAGS/LDFLAGS variables so it never picks up UBSan CFLAGS/LDFLAGS. To fix this I need to export them and update gensrc/GensrcAdlc.gmk to use them.
I am also running the build to make sure I did not miss anything. Might make more sense to insert the CFLAGS/LDFLAGS in NativeCompilation.gmk itself. Will see.