Math: fix Clang "unused but set" warnings in benchmarks.

src/Magnum/Math/Test/FunctionsBenchmark.cpp

@@ -201,6 +201,10 @@ void FunctionsBenchmark::sinCosSeparate() {
     }
 
     CORRADE_COMPARE_AS(a, 10.0f, Corrade::TestSuite::Compare::Greater);
+
+    /* To avoid the whole loop being optimized away */
+    CORRADE_VERIFY(sin == sin);
+    CORRADE_VERIFY(cos == cos);
 }
 
 void FunctionsBenchmark::sinCosCombined() {
@@ -213,6 +217,10 @@ void FunctionsBenchmark::sinCosCombined() {
     }
 
     CORRADE_COMPARE_AS(a, 10.0f, Corrade::TestSuite::Compare::Greater);
+
+    /* To avoid the whole loop being optimized away */
+    CORRADE_VERIFY(sin == sin);
+    CORRADE_VERIFY(cos == cos);
 }
 
 

src/Magnum/Math/Test/InterpolationBenchmark.cpp

@@ -70,6 +70,9 @@ void InterpolationBenchmark::baseline() {
     }
 
     CORRADE_VERIFY(!c.isNormalized());
+
+    /* To avoid "unused but set" warnings */
+    CORRADE_VERIFY(t == t);
 }
 
 void InterpolationBenchmark::quaternionLerp() {