This moves the installation of shipped source files from large
CMakeLists.txt lists to zig build recursive directory installation.
On my computer a cmake `make install` takes 2.4 seconds even when it has
to do nothing, and prints a lot of unnecessary lines to stdout that say
"up-to-date: [some file it is installing]".
After this commit, the default output of `make` is down to 1
second, and it does not print any junk to stdout. Further, a `make
install` is no longer required and `make` is sufficient.
This closes#2874.
It also closes#2585. `make` now always invokes `zig build` for
installing files and libuserland.a, and zig's own caching system makes
that go fast.
* error.BadFd is not a valid error code. it would always be a bug to
get this error code.
* merge error.Io with existing error.InputOutput
* merge error.PathNotFound with existing error.FileNotFound.
Not all OS's support both.
* add os.File.openReadC
* add error.BadPathName for windows file operations with invalid
characters
* add os.toPosixPath to help stack allocate a null terminating byte
* add some TODOs for other functions to investigate removing the
allocator requirement
* optimize some implementations to use the alternate functions when
a null byte is already available
* add a missing error.SkipZigTest
* os.selfExePath uses a non-allocating API
* os.selfExeDirPath uses a non-allocating API
* os.path.real uses a non-allocating API
* add os.path.realAlloc and os.path.realC
* convert many windows syscalls to use the W versions (See #534)
