Fix tracing problems on Windows

Warnings mess up the coverage recording process and scripts
generally shouldn't have them. If this is a problem for testing
existing scripts, they can be disabled by passing
CMAKE_UNIT_NO_DEV_WARNINGS=TRUE or
CMAKE_UNIT_NO_UNIITIALIZED_WARNINGS=TRUE

Added test coverage for past VS versions.

Fix slow builds on Windows.

Fix early truncation on Windows.