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.
