Work on CMake build system

Try to make mbedtls checks platform-independent
It seems disabling compile flags is not needed any more

ports/CMakeCommon.cmake

@@ -17,17 +17,12 @@ if(CMAKE_C_COMPILER_ID STREQUAL MSVC)
 endif()
 
 # ARM mbedtls support https://tls.mbed.org/
-if((CMAKE_C_COMPILER_ID STREQUAL Clang) OR (CMAKE_C_COMPILER_ID STREQUAL GNU))
-    set(MBEDTLSDIR ${LWIP_CONTRIB_DIR}/../mbedtls)
-    if(EXISTS ${MBEDTLSDIR}/include/mbedtls/ssl.h)
-        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-redundant-decls -DLWIP_HAVE_MBEDTLS=1")
-        
-        if(CMAKE_C_COMPILER_ID STREQUAL GNU)
-            set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-c90-c99-compat")
-        endif()
-    
-        include_directories(${MBEDTLSDIR}/include)
-        link_directories(${MBEDTLSDIR}/library)
-        link_libraries(mbedtls mbedcrypto mbedx509)
-    endif()
+set(MBEDTLSDIR ${LWIP_CONTRIB_DIR}/../mbedtls)
+if(EXISTS ${MBEDTLSDIR}/include/mbedtls/ssl.h)
+    add_definitions(-DLWIP_HAVE_MBEDTLS=1)
+
+    include_directories(${MBEDTLSDIR}/include)
+
+    link_directories(${MBEDTLSDIR}/library)
+    link_libraries(mbedtls mbedcrypto mbedx509)
 endif()