build: build with cygwin on Windows --- make CI happy

Author: zhouwg

src/llama-mmap.cpp

@@ -481,7 +481,7 @@ struct llama_mlock::impl {
         // Skip resource limit checks on visionOS/tvOS
         suggest = false;
 #else
-        struct rlimit lock_limit;
+        struct rlimit lock_limit = {};
         //if (suggest && getrlimit(RLIMIT_MEMLOCK, &lock_limit)) {
         //    suggest = false;
         //}