Disentangle from error.CurrentWorkingDirectoryUnlinked

This error is actually only ever directly returned from `std.posix.getcwd` (and only on POSIX systems, so never on Windows). Its inclusion in almost all of the error sets its currently found in is a leftover from when `std.fs.path.resolve` called `std.process.getCwdAlloc` (https://github.com/ziglang/zig/issues/13613).

lib/std/posix.zig

@@ -521,6 +521,7 @@ pub fn getppid() pid_t {
 
 pub const GetCwdError = error{
     NameTooLong,
+    /// Not possible on Windows.
     CurrentWorkingDirectoryUnlinked,
 } || UnexpectedError;
 

lib/std/process.zig

@@ -73,7 +73,10 @@ pub fn getCwd(out_buffer: []u8) GetCwdError![]u8 {
 }
 
 // Same as GetCwdError, minus error.NameTooLong + Allocator.Error
-pub const GetCwdAllocError = Allocator.Error || error{CurrentWorkingDirectoryUnlinked} || posix.UnexpectedError;
+pub const GetCwdAllocError = Allocator.Error || error{
+    /// Not possible on Windows.
+    CurrentWorkingDirectoryUnlinked,
+} || posix.UnexpectedError;
 
 /// Caller must free the returned memory.
 /// On Windows, the result is encoded as [WTF-8](https://wtf-8.codeberg.page/).
@@ -342,8 +345,6 @@ pub const SpawnError = error{
     /// Windows-only. `cwd` or `argv` was provided and it was invalid WTF-8.
     /// https://wtf-8.codeberg.page/
     InvalidWtf8,
-    /// Windows-only. `cwd` was provided, but the path did not exist when spawning the child process.
-    CurrentWorkingDirectoryUnlinked,
     /// Windows-only. NUL (U+0000), LF (U+000A), CR (U+000D) are not allowed
     /// within arguments when executing a `.bat`/`.cmd` script.
     /// - NUL/LF signifiies end of arguments, so anything afterwards

lib/std/zig/system.zig

@@ -504,7 +504,6 @@ pub fn resolveTargetQuery(io: Io, query: Target.Query) DetectError!Target {
     if (builtin.os.tag == .linux and result.isBionicLibC() and query.os_tag == null and query.android_api_level == null) {
         result.os.version_range.linux.android = detectAndroidApiLevel(io) catch |err| return switch (err) {
             error.InvalidWtf8,
-            error.CurrentWorkingDirectoryUnlinked,
             error.InvalidBatchScriptArg,
             => unreachable, // Windows-only
             error.ApiLevelQueryFailed => |e| e,

src/Compilation.zig

@@ -1851,7 +1851,6 @@ fn addModuleTableToCacheHash(
 ) error{
     OutOfMemory,
     Unexpected,
-    CurrentWorkingDirectoryUnlinked,
 }!void {
     assert(zcu.module_roots.count() != 0); // module_roots is populated
 
@@ -1919,7 +1918,6 @@ pub const CreateError = error{
     OutOfMemory,
     Canceled,
     Unexpected,
-    CurrentWorkingDirectoryUnlinked,
     /// An error has been stored to `diag`.
     CreateFail,
 };
@@ -2906,7 +2904,6 @@ pub const UpdateError = error{
     OutOfMemory,
     Canceled,
     Unexpected,
-    CurrentWorkingDirectoryUnlinked,
 };
 
 /// Detect changes to source files, perform semantic analysis, and update the output files.

src/Sema.zig

@@ -13604,10 +13604,6 @@ fn zirEmbedFile(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!A
         error.ImportOutsideModulePath => {
             return sema.fail(block, operand_src, "embed of file outside package path: '{s}'", .{name});
         },
-        error.CurrentWorkingDirectoryUnlinked => {
-            // TODO: this should be some kind of retryable failure, in case the cwd is put back
-            return sema.fail(block, operand_src, "unable to resolve '{s}': working directory has been unlinked", .{name});
-        },
         error.OutOfMemory => |e| return e,
         error.Canceled => |e| return e,
     };

src/Zcu/PerThread.zig

@@ -2388,7 +2388,6 @@ pub fn embedFile(
     OutOfMemory,
     Canceled,
     ImportOutsideModulePath,
-    CurrentWorkingDirectoryUnlinked,
 }!Zcu.EmbedFile.Index {
     const zcu = pt.zcu;
     const gpa = zcu.gpa;