hg: jdk/sandbox: 8243470: [macos] bring back O2 opt level for unsafe.cpp

[chris.hegarty at oracle.com]

Changeset: abdc7ca79bdf
Author:    vkempik
Date:      2020-06-23 13:41 +0300
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/abdc7ca79bdf

8243470: [macos] bring back O2 opt level for unsafe.cpp
Summary: Remove special case for unsafe.cpp on clang macos
Reviewed-by: erikj, ihse

! make/hotspot/lib/JvmOverrideFiles.gmk