util/signal_test.cc: suppress intentional null pointer deref

Add comment to enabele cppcheck suppression of intentional null
pointer deref via --inline-suppr option.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>

util/signal_test.cc

@@ -9,6 +9,7 @@
 namespace {
 void f0() {
   char *p = nullptr;
+  // cppcheck-suppress nullPointer
   *p = 10;  /* SIGSEGV here!! */
 }