hg: jdk/submit: 8247396: Exclude PCH for files in $(OPT_SPEED_SRC) with clang after JDK-8246751

[jiefu at tencent.com]

Changeset: 515aa4f3d9d5
Author:    jiefu
Date:      2020-06-12 10:52 +0800
URL:       https://hg.openjdk.java.net/jdk/submit/rev/515aa4f3d9d5

8247396: Exclude PCH for files in $(OPT_SPEED_SRC) with clang after JDK-8246751
Reviewed-by: ihse, erikj

! make/hotspot/lib/JvmOverrideFiles.gmk