Suppress warnings under variant=release

test/assert_test.cpp

@@ -19,7 +19,7 @@
 
 void test_default()
 {
-    int x = 1;
+    int x = 1; (void)x;
 
     BOOST_ASSERT(1);
     BOOST_ASSERT(x);

test/quick.cpp

@@ -13,6 +13,6 @@
 
 int main()
 {
-    int x = 1;
+    int x = 1; (void)x;
     BOOST_ASSERT( x == 1 );
 }