zig cc: improve linker args parsing
zig cc: improve linker args parsing

Handle linker args joined with a = like -Wl,-rpath=foo

Update existing args --major-os-version, --minor-os-version,
--major-subsystem-version and --minor-subsytem-version to work with the
new parsing.

Also handle -Wl,--script in addition to -Wl,-T

zig-lang/zig,zig-lang/zig,andrewrk/zig,andrewrk/zig,zig-lang/zig