Default to use new swift-driver to run lit tests as legacy swift driver
is deprecated for a long time. The lit tests for legacy drivers are also
disable when running new swift-driver.
Tests that relies on legacy swift driver (for example, tests merge
module) can be enabled on conditions `legacy_swift_driver`. Fix and
split up some existing tests that relies on legacy driver.
On Windows, there are multiple variants of the C runtime that must be
explicitly specified and consistently used from the runtime to the
application. The new `-libc` option allows us to control the linking
phase by correctly embedding the requested library to be linked. It is
made into a required parameter on Windows and will add in the
appropriate flags for the imported C headers as well. This ensures that
the C library is not incorrectly linked.
This flag is based on Clang's -fdebug-prefix-map, which lets the user remap absolute paths in debug info. This is necessary for reproducible builds and allows debugging to work on a different machine than the one that built the code when paths to the source may be different.
Steven Wu
Saleem Abdulrasool
David Goldman
Tony Allevato