ci: Add simple CI test

with relaxed criteria on the lingering test, as the fix is not added yet

contrib/ports/CMakeCommon.cmake

@@ -76,6 +76,8 @@ if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
     list(APPEND LWIP_COMPILER_FLAGS_GNU_CLANG
         -Wlogical-op
         -Wtrampolines
+        -fno-stack-clash-protection
+        -Wno-error=format-extra-args
     )
 
     if (NOT LWIP_HAVE_MBEDTLS)

contrib/ports/unix/check/CMakeLists.txt

@@ -16,7 +16,7 @@ include(${LWIP_DIR}/contrib/ports/CMakeCommon.cmake)
 
 if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
     # check.h causes 'error: token pasting of ',' and __VA_ARGS__ is a GNU extension' with clang 9.0.0
-    list(LWIP_COMPILER_FLAGS APPEND -Wno-gnu-zero-variadic-macro-arguments)
+    list(APPEND LWIP_COMPILER_FLAGS -Wno-gnu-zero-variadic-macro-arguments)
 endif()
 
 set (LWIP_DEFINITIONS -DLWIP_DEBUG -DLWIP_NOASSERT_ON_ERROR)

contrib/ports/unix/port/sys_arch.c

@@ -45,7 +45,6 @@
  *    leaking messages.
  */
 #define _GNU_SOURCE /* pull in pthread_setname_np() on Linux */
-
 #include "lwip/debug.h"
 
 #include <string.h>