incr-check: deal with Windows stupidity

The real problem here is that Git for Windows has horrendous defaults
which convert LF to CRLF. However, rather than changing this
configuration on the CI runners, it's worth supporting inexplicable CRLF
in these files so that anyone else cloning Zig on Windows doesn't get
unexpected test failures.

tools/incr-check.zig

@@ -660,21 +660,28 @@ const Case = struct {
                     if (root_source_file == null)
                         root_source_file = val;
 
-                    const start_index = it.index.?;
-                    const src = while (true) : (line_n += 1) {
+                    // Because Windows is so excellent, we need to convert CRLF to LF, so
+                    // can't just slice into the input here. How delightful!
+                    var src: std.ArrayListUnmanaged(u8) = .empty;
+
+                    while (true) {
                         const old = it;
-                        const next_line = it.next() orelse fatal("line {d}: unexpected EOF", .{line_n});
+                        const next_line_raw = it.next() orelse fatal("line {d}: unexpected EOF", .{line_n});
+                        const next_line = std.mem.trimRight(u8, next_line_raw, "\r");
                         if (std.mem.startsWith(u8, next_line, "#")) {
-                            const end_index = old.index.?;
-                            const src = bytes[start_index..end_index];
                             it = old;
-                            break src;
+                            break;
                         }
-                    };
+                        line_n += 1;
+
+                        try src.ensureUnusedCapacity(arena, next_line.len + 1);
+                        src.appendSliceAssumeCapacity(next_line);
+                        src.appendAssumeCapacity('\n');
+                    }
 
                     try changes.append(arena, .{
                         .name = val,
-                        .bytes = src,
+                        .bytes = src.items,
                     });
                 } else if (std.mem.eql(u8, key, "rm_file")) {
                     if (updates.items.len == 0) fatal("line {d}: rm_file directive before update", .{line_n});