Previously, it was possible to specify different debug formats for C/C++
and Swift code. In practice, binaries with both C/C++ and Swift code
would end up only having one format over the other, depending on the
exact project configuration. Since there is little value in having
separate debug information format, this changes the build configuration
to only have one debug format for both C/C++ and Swift code.
This also changes the default debug format to codeview. This is because
some of the toolchain binaries now exceed 4 GiB of dwarf debug
information, resulting in a build failure.