Enable APPLE_BUILD in makefile if using system ar
diff --git a/library/Makefile b/library/Makefile
index 857e977..353bd8b 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -22,8 +22,10 @@
 ifdef WINDOWS
 WINDOWS_BUILD=1
 else ifeq ($(shell uname -s),Darwin)
+ifeq ($(AR),ar)
 APPLE_BUILD ?= 1
 endif
+endif
 
 # To compile as a shared library:
 ifdef SHARED