RTEMS 5.x moved the PC BSP to 686. This commit makes the EPICS
target match; RTEMS-pc386 and the -qemu variant can only be built
when RTEMS_VERSION != 5, whereas RTEMS-pc686 and its -qemu version
will only build when RTEMS_VERSION == 5 (there are checks with
descriptive errors included).
makeTestFile.pl was also reformatted and modified to use exec to
run tests on non-Windows hosts as required by the Perl test harness.
zimoch
