Don't rely on SIGILL to detect AVX2 support in Sulong test.

Author: rschatz

sulong/tests/com.oracle.truffle.llvm.tests.sulongavx.native/avx/avx2fallback.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2020, Oracle and/or its affiliates.
+ * Copyright (c) 2018, 2025, Oracle and/or its affiliates.
  *
  * All rights reserved.
  *
@@ -28,7 +28,6 @@
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #include <stdio.h>
-#include "../avx2fallback.h"
 
 int avx2_fallback() {
     printf("v3: -1 -1 -1 -1\n");
@@ -39,13 +38,17 @@ int avx2_fallback() {
 typedef int vec4 __attribute__((vector_size(16)));
 
 int main() {
+#if defined(__AVX2__)
     volatile vec4 v1 = { -1, 8, 2, -5 };
 
     volatile vec4 v3 = __builtin_shufflevector(v1, v1, 0, 0, 0, 0);
     printf("v3: %d %d %d %d\n", v3[0], v3[1], v3[2], v3[3]);
 
     volatile vec4 v4 = __builtin_shufflevector(v1, v1, 3, 2, 1, 0);
     printf("v4: %d %d %d %d\n", v4[0], v4[1], v4[2], v4[3]);
+#else
+    avx2_fallback();
+#endif
 
     return 0;
 }