cmake: initialize internal `CURL_INCLUDES` variable

Closes #20451

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5fd729f1bd6eafd5312910de7d2c12c30a28c364..755835ece3f00eebb21e93d87b0050a73b971a00 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1442,6 +1442,8 @@ if(WIN32)
   option(CURL_CA_SEARCH_SAFE "Enable safe CA bundle search (within the curl tool directory) on Windows" OFF)
 endif()
 
+set(CURL_INCLUDES "")
+
 # Check for header files
 if(WIN32)
   list(APPEND CURL_INCLUDES "winsock2.h")