Return FileNotFound when CreateProcessW is called with a missing path

[phatchman]

Fixes #19023

CreateProcessW currently returns error.Unexpected when the lpCurrentDirectory value is a directory that does not exist.
With this PR, CreateProcessW returns error.FileNotFound in those cases.

Directory not existing and directory invalid cannot be distinguished. CreateProcessW returns [ERROR_DIRECTORY - 267 (0x10B) - The directory name is invalid.] in both cases.

Can be tested with the following test.

test "test CreateProcessW with invalid path" {
    const allocator = std.testing.allocator;
    const application_name = try std.unicode.utf8ToUtf16LeAllocZ(allocator, "c:\\windows\\explorer.exe");
    defer allocator.free(application_name);
    const command_line = try std.unicode.utf8ToUtf16LeAllocZ(allocator, "");
    defer allocator.free(command_line);
    const startup_directory = try std.unicode.utf8ToUtf16LeAllocZ(allocator, "c:\\directory_that_does_not_exist");
    defer allocator.free(startup_directory);

    var startup_info = std.mem.zeroes(std.os.windows.STARTUPINFOW);
    var process_info = std.mem.zeroes(std.os.windows.PROCESS_INFORMATION);
    const inherit: std.os.windows.BOOL = 0;
    const flags = std.mem.zeroes(std.os.windows.CreateProcessFlags);

    try std.testing.expectError(error.FileNotFound, std.os.windows.CreateProcessW(
        application_name,
        command_line,
        null,
        null,
        inherit,
        flags,
        null,
        startup_directory,
        &startup_info,
        &process_info,
    ));
}
const std = @import("std");

[squeek502]

Nice , thanks for the fix! Would be good to add a test for this to the windows_spawn standalone test

Something like:

try std.testing.expectError(error.FileNotFound, testExecWithCwd(allocator, "hello.exe", "missing_dir", ""));

after these lines

[phatchman]

Test added and confirmed that all standalone tests pass.

I'm new to making PRs, so please let me know if I've done this right or whether I should have made a single commit with all the changes?

[alexrp]

I'm new to making PRs, so please let me know if I've done this right or whether I should have made a single commit with all the changes?

For future reference, it's generally best to add the test in the same commit that makes the change being tested. But since this is a fairly small/focused PR, we can just squash the two commits when merging, so no big deal.