hg: jdk/jdk: 8245137: aarch64 ICache flush depends on enabling gnu extensions

[kim.barrett at oracle.com]

Changeset: f814dd59bfe9
Author:    kbarrett
Date:      2020-05-18 10:47 -0400
URL:       https://hg.openjdk.java.net/jdk/jdk/rev/f814dd59bfe9

8245137: aarch64 ICache flush depends on enabling gnu extensions
Summary: Use __builtin___clear_cache.
Reviewed-by: aph, dholmes

! src/hotspot/cpu/aarch64/icache_aarch64.hpp