Fix offline builds OWN_CURL_SOURCE_DIR

ext/curl.cmake

@@ -13,9 +13,15 @@ else()
     endif()
 endif()
 
+if(OWN_CURL_SOURCE_DIR)
+    set(CURL_EXT_PROPERTIES SOURCE_DIR ${OWN_CURL_SOURCE_DIR})
+else()
+    set(CURL_EXT_PROPERTIES URL "http://curl.haxx.se/download/curl-8.0.1.tar.gz")
+endif()
+
 ExternalProject_Add(
         curl_ext
-        URL "http://curl.haxx.se/download/curl-8.0.1.tar.gz"
+        ${CURL_EXT_PROPERTIES}
         INSTALL_DIR ${CMAKE_BINARY_DIR}/ext/curl
         CMAKE_ARGS "-DCMAKE_INSTALL_PREFIX=${CMAKE_BINARY_DIR}/ext/curl" "-DBUILD_CURL_EXE=OFF" "-DBUILD_SHARED_LIBS=OFF" "-DCURL_STATICLIB=ON" "-DCURL_DISABLE_LDAP=ON" "-DCURL_USE_LIBSSH2=OFF" "-DCURL_USE_OPENLDAP=OFF" "-DUSE_LIBIDN2=OFF" "-DENABLE_WEBSOCKETS=ON" "-DCMAKE_C_FLAGS=${CMAKE_C_FLAGS}" "-DCMAKE_LINK_FLAGS=${CMAKE_LINK_FLAGS}" "-DCMAKE_LIBRARY_ARCHITECTURE=${CMAKE_LIBRARY_ARCHITECTURE}" ${CURL_EXT_EXTRA_OPTIONS}
 )