Now that the linkers are split out of the compilers this enum is
only used to know what platform we're compiling for. Which is
what the MachineInfo class is for
Instead of the DynamicLinker returning a hardcoded value like
`-Wl,-foo`, it now is passed a value that could be '-Wl,', or could be
something '-Xlinker='
This makes a few things cleaner, and will make it possible to fix using
clang (not clang-cl) on windows, where it invokes either link.exe or
lld-link.exe instead of a gnu-ld compatible linker.
There are two problems, one is that it assumes -flto is the argument
to do LTO/WPO, which isn't true of ICC and MSVC (and presumably)
others. It's also incorrect because it assumes that the compiler and
linker will always be the same, which isn't necessarily true. You
could combine GCC with Apple's linker, or clang with link.exe, which
use different arguments.
There is a pretty big error in here, trying to return a tuple
comperhension: (a for a in []) is not a tuple, it's a generator. This
has profound type annotations: generators don't support most tuple or
list methods, and they can only be iterated once. Beyond that tuples are
meant for heterogenous types, ie, position matters for types. I've
converted the output to a list in all cases.