disable behavior test for 128-bit cmpxchg

once #2883 is done this can be revisited

Author: andrewrk

test/stage1/behavior/atomics.zig

@@ -70,22 +70,23 @@ test "cmpxchg with ptr" {
     expect(x == &data2);
 }
 
-test "128-bit cmpxchg" {
-    if (builtin.arch != .x86_64) {
-        return error.SkipZigTest;
-    }
-    var x: u128 align(16) = 1234; // TODO: https://github.com/ziglang/zig/issues/2987
-    if (@cmpxchgWeak(u128, &x, 99, 5678, .SeqCst, .SeqCst)) |x1| {
-        expect(x1 == 1234);
-    } else {
-        @panic("cmpxchg should have failed");
-    }
-
-    while (@cmpxchgWeak(u128, &x, 1234, 5678, .SeqCst, .SeqCst)) |x1| {
-        expect(x1 == 1234);
-    }
-    expect(x == 5678);
-
-    expect(@cmpxchgStrong(u128, &x, 5678, 42, .SeqCst, .SeqCst) == null);
-    expect(x == 42);
-}
+// TODO this test is disabled until this issue is resolved:
+// https://github.com/ziglang/zig/issues/2883
+// otherwise cross compiling will result in:
+// lld: error: undefined symbol: __sync_val_compare_and_swap_16
+//test "128-bit cmpxchg" {
+//    var x: u128 align(16) = 1234; // TODO: https://github.com/ziglang/zig/issues/2987
+//    if (@cmpxchgWeak(u128, &x, 99, 5678, .SeqCst, .SeqCst)) |x1| {
+//        expect(x1 == 1234);
+//    } else {
+//        @panic("cmpxchg should have failed");
+//    }
+//
+//    while (@cmpxchgWeak(u128, &x, 1234, 5678, .SeqCst, .SeqCst)) |x1| {
+//        expect(x1 == 1234);
+//    }
+//    expect(x == 5678);
+//
+//    expect(@cmpxchgStrong(u128, &x, 5678, 42, .SeqCst, .SeqCst) == null);
+//    expect(x == 42);
+//}