Previously the zig build system incorrectly assumed that the only build
artifact was a binary. Now, when you enable the cache, only the output
dir is printed to stdout, and the zig build system iterates over the
files in that directory, copying them to the output directory.
To support this change:
* Add `std.os.renameat`, `std.os.renameatZ`, and `std.os.renameatW`.
* Fix `std.os.linux.renameat` not compiling due to typos.
* Deprecate `std.fs.updateFile` and `std.fs.updateFileMode`.
* Add `std.fs.Dir.updateFile`, which supports using open directory
handles for both the source and destination paths, as well as an
options parameter which allows overriding the mode.
* Update `std.fs.AtomicFile` to support operating based on an open
directory handle. Instead of `std.fs.AtomicFile.init`, use
`std.fs.Dir.atomicFile`.
* `std.fs.AtomicFile` deinit() better handles the situation when the
rename fails but the temporary file still exists, by still
attempting to remove the temporary file.
* `std.fs.Dir.openFileWindows` is moved to `std.os.windows.OpenFileW`.
* `std.os.RenameError` gains the error codes `NoDevice`,
`SharingViolation`, and `PipeBusy` which have been observed from
Windows.
Closes#4733
std.os.getenv and std.os.getenvZ have nice compile errors when not linking
libc and using Windows.
std.os.getenvW is provided as a Windows-only API that does not require
an allocator. It uses the Process Environment Block.
std.process.getEnvVarOwned is improved to be a simple wrapper on top of
std.os.getenvW.
std.process.getEnvMap is improved to use the Process Environment Block
rather than calling GetEnvironmentVariableW.
std.zig.system.NativePaths uses process.getEnvVarOwned instead of
std.os.getenvZ, which works on Windows as well as POSIX.
The actual desired access mask in this case seems quite confusing and badly documented. The previous combination of `GENERIC_READ` and `SYNCHRONIZE` seems both illegal and redundant according to the [`ntifs.h` documentation](https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/nf-ntifs-ntcreatefile), which specifies that `GENERIC_READ` should not be used for directories and includes `SYNCHRONIZE`. `winnt.h` contains a number of relevant-sounding flags such as `FILE_ADD_FILE`, `FILE_ADD_SUBDIRECTORY`, and `FILE_DELETE_CHILD` that do not show up in documentation at all. These are equal in value to file-specific flags that are documented as flags you should not specify when opening a directory.
