Build error with lastest zig

[jimying]

Zig Version

0.12.0-dev.1663+6b1a823b2

Zig Language Server Version

e89b712

Steps to Reproduce

Due to the zig new feature: ziglang/zig#18017 (zig commit: 6b1a823b2),
which strictly check var, and throw "error: local variable is never mutated"

Use lastest zig (build from zig source) to build zls, build error as follow.

build error log for zls_gen:

src/config_gen/config_gen.zig:270:9: error: local variable is never mutated
    var writer = buffered_writer.writer();
        ^~~~~~
src/config_gen/config_gen.zig:270:9: note: consider using 'const'
src/config_gen/config_gen.zig:556:25: error: local variable is never mutated
                    var content_token = tokenizer.next();
                        ^~~~~~~~~~~~~
src/config_gen/config_gen.zig:556:25: note: consider using 'const'
src/config_gen/config_gen.zig:887:13: error: local variable is never mutated
        var arguments = try extractArgumentsFromSignature(allocator, signature[builtin.name.len + 1 ..]);
            ^~~~~~~~~
src/config_gen/config_gen.zig:887:13: note: consider using 'const'
src/config_gen/config_gen.zig:849:9: error: local variable is never mutated
    var builtins = try collectBuiltinData(allocator, version, langref_source);
        ^~~~~~~~
src/config_gen/config_gen.zig:849:9: note: consider using 'const'
src/config_gen/config_gen.zig:973:9: error: local variable is never mutated
    var gpa = general_purpose_allocator.allocator();
        ^~~
src/config_gen/config_gen.zig:973:9: note: consider using 'const'

I try fix zls_gen errors, throw more errors:

/env/.home/d/.cache/zig/p/1220bb12c9bfe291eed1afe6a2070c7c39918ab1979f24a281bba39dfb23f5bcd544/known-folders.zig:35:9: error: local variable is never mutated
    var path_or_null = try getPath(allocator, folder);
        ^~~~~~~~~~~~
/env/.home/d/.cache/zig/p/1220bb12c9bfe291eed1afe6a2070c7c39918ab1979f24a281bba39dfb23f5bcd544/known-folders.zig:35:9: note: consider using 'const'
/env/.home/d/.cache/zig/p/1220bb12c9bfe291eed1afe6a2070c7c39918ab1979f24a281bba39dfb23f5bcd544/known-folders.zig:180:21: error: local variable is never mutated
                var subdir = line[start..end];
                    ^~~~~~
/env/.home/d/.cache/zig/p/1220bb12c9bfe291eed1afe6a2070c7c39918ab1979f24a281bba39dfb23f5bcd544/known-folders.zig:180:21: note: consider using 'const'
/env/.home/d/.cache/zig/p/1220bb12c9bfe291eed1afe6a2070c7c39918ab1979f24a281bba39dfb23f5bcd544/known-folders.zig:341:13: error: local variable is never mutated
        var path_or_null = try getPath(std.testing.allocator, @field(KnownFolder, fld.name));
            ^~~~~~~~~~~~
/env/.home/d/.cache/zig/p/1220bb12c9bfe291eed1afe6a2070c7c39918ab1979f24a281bba39dfb23f5bcd544/known-folders.zig:341:13: note: consider using 'const'
src/offsets.zig:116:13: error: local variable is never mutated
        var token_start = tokens_start[upper_index];
            ^~~~~~~~~~~
src/offsets.zig:116:13: note: consider using 'const'
src/Server.zig:1609:9: error: local variable is never mutated
    var result = try arena.alloc(std.meta.Child(std.meta.Child(Result)), actions.items.len);
        ^~~~~~
src/Server.zig:1609:9: note: consider using 'const'
/env/.home/d/.cache/zig/p/1220363c7e27b2d3f39de6ff6e90f9537a0634199860fea237a55ddb1e1717f5d6a5/binned_allocator.zig:496:9: error: local variable is never mutated
    var slice = try allocator.alloc(u8, 8192 + 50);
        ^~~~~
/env/.home/d/.cache/zig/p/1220363c7e27b2d3f39de6ff6e90f9537a0634199860fea237a55ddb1e1717f5d6a5/binned_allocator.zig:496:9: note: consider using 'const'
src/DocumentScope.zig:681:25: error: local variable is never mutated
                    var gop_res = try context.doc_scope.enum_completions.getOrPut(allocator, .{
                        ^~~~~~~
src/DocumentScope.zig:681:25: note: consider using 'const'
src/analysis.zig:199:17: error: local variable is never mutated
            var end_token = ast.lastToken(tree, param.type_expr);
                ^~~~~~~~~
src/analysis.zig:199:17: note: consider using 'const'
src/analysis.zig:1496:21: error: local variable is never mutated
                var lhs = (try analyser.resolveTypeOfNodeInternal(.{
                    ^~~
src/analysis.zig:1496:21: note: consider using 'const'
src/analysis.zig:2402:25: error: local variable is never mutated
                    var import_str = offsets.locToSlice(tokenizer.buffer, .{
                        ^~~~~~~~~~
src/analysis.zig:2402:25: note: consider using 'const'
src/analysis.zig:2399:25: error: local variable is never mutated
                    var import_str_tok = tokenizer.next(); // should be the .string_literal
                        ^~~~~~~~~~~~~~
src/analysis.zig:2399:25: note: consider using 'const'
src/analysis.zig:2745:9: error: local variable is never mutated
    var held_line = try allocator.dupeZ(u8, offsets.locToSlice(text, line_loc));
        ^~~~~~~~~
src/analysis.zig:2745:9: note: consider using 'const'
src/analysis.zig:2566:9: error: local variable is never mutated
    var line = offsets.locToSlice(text, line_loc);
        ^~~~
src/analysis.zig:2566:9: note: consider using 'const'

Expected Behavior

build successful

Actual Behavior

[xdBronch]

#1605 should fix this