zig fetch: add missing path separator in error message

Signed-off-by: Tw <[email protected]>

src/Package/Fetch.zig

@@ -609,7 +609,7 @@ fn loadManifest(f: *Fetch, pkg_root: Cache.Path) RunError!void {
     ast.* = try std.zig.Ast.parse(arena, manifest_bytes, .zon);
 
     if (ast.errors.len > 0) {
-        const file_path = try std.fmt.allocPrint(arena, "{}" ++ Manifest.basename, .{pkg_root});
+        const file_path = try std.fmt.allocPrint(arena, "{}" ++ fs.path.sep_str ++ Manifest.basename, .{pkg_root});
         try std.zig.putAstErrorsIntoBundle(arena, ast.*, file_path, eb);
         return error.FetchFailed;
     }
@@ -783,7 +783,7 @@ fn srcLoc(
     const eb = &f.error_bundle;
     const token_starts = ast.tokens.items(.start);
     const start_loc = ast.tokenLocation(0, tok);
-    const src_path = try eb.printString("{}" ++ Manifest.basename, .{f.parent_package_root});
+    const src_path = try eb.printString("{}" ++ fs.path.sep_str ++ Manifest.basename, .{f.parent_package_root});
     const msg_off = 0;
     return eb.addSourceLocation(.{
         .src_path = src_path,