Revert "move to stage2 (#781)" (#783)

This reverts commit 29679ee6f8.

build.zig

@@ -13,6 +13,7 @@ pub fn build(b: *std.build.Builder) !void {
 
     const mode = b.standardReleaseOptions();
     const exe = b.addExecutable("zls", "src/main.zig");
+    exe.use_stage1 = true;
     const exe_options = b.addOptions();
     exe.addOptions("build_options", exe_options);
 
@@ -133,6 +134,7 @@ pub fn build(b: *std.build.Builder) !void {
         });
     }
 
+    tests.use_stage1 = true;
     tests.addPackage(.{ .name = "zls", .source = .{ .path = "src/zls.zig" }, .dependencies = exe.packages.items });
     tests.setBuildMode(.Debug);
     tests.setTarget(target);