This is a smoke test of the SSA renamer's local variable preserver.
It tests a case observed from Scala, wherein a local variable is assigned
an identical value twice. The correct result should be only a single
mark-local, with the second assignment eaten by copy-propogation.
This test compares emitted code against a known-good (via eyeballing)
version, so it is possible for this test to spuriously fail if other
aspects of conversion end up altering the output in innocuous ways.