make sure PrettyTextReporter is in pretty mode when under test.

These tests where failing when run from the command line via `./build.sh
TEST_AFTER_BUILD=YES`.  The PrettyTextReporter was falling back to plain
mode since isatty() was returning NO.
for OSX tests, tests should be run from the project's directory.

For OSX tests only, Xcode will chdir to the project's directory before
running the tests.  If the test bundle is at '/a/b/b.xcodeproj', then
xcode will change to '/a/b' first.