Hello-

I get a different number of test results from libphobos.unittest/unittest.exp,
depending on server load. I believe it's because this testsuite doesn't check
runtest_file_p:

$ make -j 1 RUNTESTFLAGS='unittest.exp' check-target-libphobos | grep '^#'
 # of expected passes           10

$ make -j 2 RUNTESTFLAGS='unittest.exp' check-target-libphobos | grep '^#'
 # of expected passes           10
 # of expected passes           10

$ make -j 4 RUNTESTFLAGS='unittest.exp' check-target-libphobos | grep '^#'
 # of expected passes           10
 # of expected passes           10
 # of expected passes           10
 # of expected passes           10

When running in parallel along with other tests, even at a fixed argument
for -j, the number of tests that actually execute will depend on how many of the
parallel sub-makes happened to start prior to the first one finishing, hence
it changes from run to run.

The attached patch fixes it for me, if it looks OK? Thanks, this would remove
some noise from before/after test comparisons.

-Lewis