Adds curl to the list of system libraries

Fixes macOS build with system libcurl

cmake-proxies/cmake-modules/dependencies/curl.cmake

@@ -0,0 +1,30 @@
+if( ${_OPT}use_curl STREQUAL "system" )
+    # On macOS - CURL::libcurl is not defined by FindCURL for some reason
+
+    if(NOT TARGET CURL::libcurl)
+        add_library(CURL::libcurl UNKNOWN IMPORTED)
+        set_target_properties(CURL::libcurl PROPERTIES
+        INTERFACE_INCLUDE_DIRECTORIES "${CURL_INCLUDE_DIRS}")
+
+        if(EXISTS "${CURL_LIBRARY}")
+            set_target_properties(CURL::libcurl PROPERTIES
+                IMPORTED_LINK_INTERFACE_LANGUAGES "C"
+                IMPORTED_LOCATION "${CURL_LIBRARY}")
+        endif()
+
+        if(CURL_LIBRARY_RELEASE)
+            set_property(TARGET CURL::libcurl APPEND PROPERTY
+                IMPORTED_CONFIGURATIONS RELEASE)
+            set_target_properties(CURL::libcurl PROPERTIES
+                IMPORTED_LINK_INTERFACE_LANGUAGES "C"
+                IMPORTED_LOCATION_RELEASE "${CURL_LIBRARY_RELEASE}")
+        endif()
+        if(CURL_LIBRARY_DEBUG)
+            set_property(TARGET CURL::libcurl APPEND PROPERTY
+                IMPORTED_CONFIGURATIONS DEBUG)
+            set_target_properties(CURL::libcurl PROPERTIES
+                IMPORTED_LINK_INTERFACE_LANGUAGES "C"
+                IMPORTED_LOCATION_DEBUG "${CURL_LIBRARY_DEBUG}")
+        endif()
+    endif()
+endif()