tests/common/124: Print an error when square fails

Otherwise we can't know why it failed and that makes it harder to debug.

test cases/common/126 llvm ir and assembly/main.c

@@ -1,9 +1,14 @@
+#include <stdio.h>
+
 unsigned square_unsigned (unsigned a);
 
 int
 main (int argc, char * argv[])
 {
-  if (square_unsigned (2) != 4)
-    return -1;
+  unsigned int ret = square_unsigned (2);
+  if (ret != 4) {
+    printf("Got %u instead of 4\n", ret);
+    return 1;
+  }
   return 0;
 }

test cases/common/126 llvm ir and assembly/main.cpp

@@ -1,3 +1,4 @@
+#include <stdio.h>
 
 extern "C" {
   unsigned square_unsigned (unsigned a);
@@ -6,7 +7,10 @@ extern "C" {
 int
 main (int argc, char * argv[])
 {
-  if (square_unsigned (2) != 4)
-    return -1;
+  unsigned int ret = square_unsigned (2);
+  if (ret != 4) {
+    printf("Got %u instead of 4\n", ret);
+    return 1;
+  }
   return 0;
 }