hg: build-infra/jdk9: In ExecuteWithLog, read cmdline file with cat for logging, to keep debug

[magnus.ihse.bursie at oracle.com]

Changeset: 57a9f4f8db17
Author:    ihse
Date:      2016-01-30 09:02 +0100
URL:       http://hg.openjdk.java.net/build-infra/jdk9/rev/57a9f4f8db17

In ExecuteWithLog, read cmdline file with cat for logging, to keep debug
logs more readable.

! make/common/MakeBase.gmk