Avoid "function 'testDynamicCast()::S1::~S1' has internal linkage...

...but is not defined"

Change-Id: Ib1350d5d34eef0d544ca8f436ae63c693b7d2f5d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155354
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

compilerplugins/clang/test/redundantcast.cxx

@@ -348,7 +348,7 @@ void testSuspiciousReinterpretCast() {
 
 void testDynamicCast() {
 
-    struct S1 { virtual ~S1(); };
+    struct S1 { virtual ~S1() {} };
     struct S2 final: S1 {};
     struct S3: S1 {};