cmake: build tests last

Keep -Werror for src, contrib and do not pass it for tests/

CMakeLists.txt

@@ -147,6 +147,7 @@ set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 enable_testing()
 
 option(BUILD_DOCUMENTATION "Build the Doxygen documentation." ON)
+option(BUILD_TESTS "Build tests." OFF)
 
 # Check whether we're on a 32-bit or 64-bit system
 if(CMAKE_SIZEOF_VOID_P EQUAL "8")
@@ -704,20 +705,13 @@ if(SODIUM_LIBRARY)
   set(ZMQ_LIB "${ZMQ_LIB};${SODIUM_LIBRARY}")
 endif()
 
-option(BUILD_TESTS "Build tests." OFF)
+add_subdirectory(contrib)
+add_subdirectory(src)
 
 if(BUILD_TESTS)
   add_subdirectory(tests)
 endif()
 
-# warnings are cleared only for GCC on Linux
-if (NOT (MINGW OR APPLE OR FREEBSD OR OPENBSD OR DRAGONFLY))
-add_compile_options("${WARNINGS_AS_ERRORS_FLAG}") # applies only to targets that follow
-endif()
-
-add_subdirectory(contrib)
-add_subdirectory(src)
-
 if(BUILD_DOCUMENTATION)
   set(DOC_GRAPHS "YES" CACHE STRING "Create dependency graphs (needs graphviz)")
   set(DOC_FULLGRAPHS "NO" CACHE STRING "Create call/callee graphs (large)")