Fixed Android clang warning.

imgui_draw.cpp

@@ -42,7 +42,9 @@
 #pragma clang diagnostic ignored "-Wfloat-equal"            // warning : comparing floating point with == or != is unsafe   // storing and comparing against same constants ok.
 #pragma clang diagnostic ignored "-Wglobal-constructors"    // warning : declaration requires a global destructor           // similar to above, not sure what the exact difference it.
 #pragma clang diagnostic ignored "-Wsign-conversion"        // warning : implicit conversion changes signedness             //
+#if __has_warning("-Wcomma")
 #pragma clang diagnostic ignored "-Wcomma"                  // warning : possible misuse of comma operator here             //
+#endif
 #if __has_warning("-Wreserved-id-macro")
 #pragma clang diagnostic ignored "-Wreserved-id-macro"      // warning : macro name is a reserved identifier                //
 #endif