pragma warning bug fix when using g++ on windows (assimp#5943)

Author: stekap000

contrib/poly2tri/poly2tri/common/shapes.h

@@ -38,8 +38,7 @@
 #include <stdexcept>
 #include <vector>
 
-
-#if defined(_WIN32)
+#if defined(_WIN32) && defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning( disable: 4251)
 #endif
 namespace p2t {