Merge pull request #2629 from okuoku/silence-cygwin-warning

Set CMake policy CMP0054 to NEW to silence warning
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 70fe3fe..0600516 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -37,6 +37,9 @@
 if (POLICY CMP0048)
   cmake_policy(SET CMP0048 NEW)
 endif()
+if(POLICY CMP0054)
+  cmake_policy(SET CMP0054 NEW)
+endif()
 
 project(glslang LANGUAGES CXX)