Autodetect if running on OS X in makefile
diff --git a/library/Makefile b/library/Makefile
index 9affde4..89bc84f 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -21,7 +21,7 @@
 # if were running on Windows build for Windows
 ifdef WINDOWS
 WINDOWS_BUILD=1
-else ifdef APPLE
+else ifeq ($(shell uname -s),Darwin)
 APPLE_BUILD=1
 endif