hg: jdk/jdk: 8210164: building Minimal VM fails with error: comparison of unsigned expression < 0 is always false [-Werror=type-limits]

[kim.barrett at oracle.com]

Changeset: 3198179d97fa
Author:    avoitylov
Date:      2018-08-30 16:33 -0400
URL:       http://hg.openjdk.java.net/jdk/jdk/rev/3198179d97fa

8210164: building Minimal VM fails with error: comparison of unsigned expression < 0 is always false [-Werror=type-limits]
Summary: Conditionalize compare with serial_phase_count.
Reviewed-by: kbarrett, shade

! src/hotspot/share/gc/shared/weakProcessorPhases.cpp