behavior: work around LLVM bug

See #18034

Author: mlugg

test/behavior/align.zig

@@ -581,6 +581,10 @@ test "comptime alloc alignment" {
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_llvm and builtin.target.cpu.arch == .x86) {
+        // https://github.com/ziglang/zig/issues/18034
+        return error.SkipZigTest;
+    }
 
     comptime var bytes1 = [_]u8{0};
     _ = &bytes1;