[Truffle] Add MRI test profile to pom files.

[bjfish]

With workarounds (after current MRI test issues are fixed) mvn -Ptruffle-mri-test completes with:

     [exec] Finished tests in 43.266000s, 38.5291 tests/s, 3727.0836 assertions/s.
     [exec] 
     [exec] 1667 tests, 161256 assertions, 0 failures, 0 errors, 1

[chrisseaton]

This is great. Do you know off the top of your head how many assertions there are? Is 161k 0.1%? 10%

[bjfish]

@chrisseaton
161256 / 1099625 = 14.664635671 %
jruby has the following

6517 tests, 1099625 assertions, 0 failures, 0 errors, 16 skips

[bjfish]

@eregon I updated this to use ruby from the system path to run tool/jt.rb.