In an MSVC context, `-MT` means
"Use static run-time"
and it is a flag with no parameter.
On POSIX it means
"Specify name of main file output in depfile"
and it is "joined or separate".
The former was interfering with the latter. Now, the MT flag is required
to be specified with a `/` to disambiguate: `/MT`.
This caused link errors in c++ code because it was not correct to pass
these flags to child codegens. And that was the only reason to detect
these flags. Otherwise we can safely rely on non-explicitly-detected
flag forwarding.
This is only the first step; it makes zig cc recognize -z and append it to the linker args, but the linker arg parsing doesn't support -z yet so it will just give the warning 'unsupported linker arg: -z'
* The generated options data file is sorted now in a way that
makes sure longer prefixes are first. This prevents collisions
with some parameters.
* Add support for `-fPIC`, `-fno-PIC`, `-nostdlib`, `-shared`,
`-rdynamic`, `-Wl,-soname`, `-Wl,-rpath`
* Better support for `-o`.
* Disable generating h files
* Shared library support.
* Better positional argument support.
Andrew Kelley