Some hotspot testcase scripts check for a file JDK64BIT in the home directory, and
use the contents as command-line arguments to the JVM. Without this they never
test 64-bit mode (at least on Solaris).

The JDK6BIT file's contents are expected to be -d64 to ensure the 64-bit
JDK is executed.

JPRT does not use this file convention, so some tests are not testing
64-bit mode.

The scripts should use TESTVMOPTS instead, which jtreg sets. This will
contain -d64 when JPRT/JTREG is testing a 64-bit JVM.