Conditionally assign APPLE_BUILD var in makefile
diff --git a/library/Makefile b/library/Makefile
index 89bc84f..b1ef8d3 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -22,7 +22,7 @@
 ifdef WINDOWS
 WINDOWS_BUILD=1
 else ifeq ($(shell uname -s),Darwin)
-APPLE_BUILD=1
+APPLE_BUILD ?= 1
 endif
 
 # To compile as a shared library: