goto-cc/gcc command line: add option coverage

GCC supports -coverage to enable coverage instrumentation. For now, we
silently ignore this option to avoid warnings about an unsupported
option. We could, however, consider inserting coverage instrumentation
as --cover does with goto-instrument or cbmc.

Author: tautschnig

src/goto-cc/gcc_cmdline.cpp

@@ -216,6 +216,7 @@ const char *gcc_options_without_argument[]=
   "-EB",
   "-EL",
   "-fast", // Apple only
+  "-coverage",
   nullptr
 };
 // clang-format on