Revert "Merge pull request #17637 from jacobly0/x86_64-test-std"

This reverts commit 0c99ba1eab, reversing
changes made to 5f92b070bf.

This caused a CI failure when it landed in master branch due to a
128-bit `@byteSwap` in std.mem.

lib/std/json.zig

@@ -9,7 +9,6 @@
 //! The low-level `writeStream` emits syntax-conformant JSON tokens to a `std.io.Writer`.
 //! The high-level `stringify` serializes a Zig or `Value` type into JSON.
 
-const builtin = @import("builtin");
 const testing = @import("std").testing;
 const ArrayList = @import("std").ArrayList;
 
@@ -24,8 +23,6 @@ test Scanner {
 }
 
 test parseFromSlice {
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
-
     var parsed_str = try parseFromSlice([]const u8, testing.allocator, "\"a\\u0020b\"", .{});
     defer parsed_str.deinit();
     try testing.expectEqualSlices(u8, "a b", parsed_str.value);
@@ -38,16 +35,12 @@ test parseFromSlice {
 }
 
 test Value {
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
-
     var parsed = try parseFromSlice(Value, testing.allocator, "{\"anything\": \"goes\"}", .{});
     defer parsed.deinit();
     try testing.expectEqualSlices(u8, "goes", parsed.value.object.get("anything").?.string);
 }
 
 test writeStream {
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
-
     var out = ArrayList(u8).init(testing.allocator);
     defer out.deinit();
     var write_stream = writeStream(out.writer(), .{ .whitespace = .indent_2 });
@@ -65,8 +58,6 @@ test writeStream {
 }
 
 test stringify {
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
-
     var out = ArrayList(u8).init(testing.allocator);
     defer out.deinit();