Normalize line endings in testBuildTripleString()

This change normalizes the line endings of expected and result strings in Erfurt_Store_Adapter_VirtuosoIntegrationTest::testBuildTripleString() before performing the comparison.

Without normalization this test fails on Windows systems as buildTripleString() uses the platform dependent PHP_EOL to combine statements, whereas the hardcoded expections in the test file use "\n" line endings.