Add option for suppression file in valgrind memcheck [AP-3695] (#185)

Valgrind memcheck supports suppression files. This change allows using
our cmake logic to specify a suppression file relative to the repo root.

Tested: swift-nav/starling#9972

Author: sbmueller

Valgrind.cmake

@@ -294,7 +294,7 @@ endmacro()
 
 function(swift_add_valgrind_memcheck target)
   set(argOption SHOW_REACHABLE TRACK_ORIGINS UNDEF_VALUE_ERRORS GENERATE_JUNIT_REPORT)
-  set(argSingle LEAK_CHECK)
+  set(argSingle LEAK_CHECK SUPPRESSIONS_FILE)
   set(argMulti JUNIT_OPTIONS)
 
   set(valgrind_tool memcheck)
@@ -322,6 +322,10 @@ function(swift_add_valgrind_memcheck target)
     list(APPEND valgrind_tool_options "--leak-check=${x_LEAK_CHECK}")
   endif()
 
+  if (x_SUPPRESSIONS_FILE)
+    list(APPEND valgrind_tool_options "--suppressions=${CMAKE_SOURCE_DIR}/${x_SUPPRESSIONS_FILE}")
+  endif()
+
   setup_custom_target(${valgrind_tool} ${target_name})
 
   if (x_GENERATE_JUNIT_REPORT)