tests/frontend: Test that platform select has expected default value
tests/frontend: Test that platform select has expected default value

squat/tectonic-installer,cpanato/tectonic-installer,lander2k2/tectonic-installer,lander2k2/tectonic-installer,cpanato/tectonic-installer,kyoto/tectonic-installer,kyoto/tectonic-installer,kalmog/tectonic-installer,kyoto/tectonic-installer,kyoto/tectonic-installer,derekhiggins/installer,squat/tectonic-installer,lander2k2/tectonic-installer,kalmog/tectonic-installer,kalmog/tectonic-installer,cpanato/tectonic-installer,cpanato/tectonic-installer,lander2k2/tectonic-installer,squat/tectonic-installer,squat/tectonic-installer,derekhiggins/installer,kyoto/tectonic-installer