Unbreak Darwin build

-lOpenCL should be removed from LDLIBS on Darwin. Use a trick similar
to the one used for OS-specific inclusions to remove the unwated
include.

Makefile

@@ -18,17 +18,19 @@ SPARSEFLAGS=-Wsparse-all -Wno-decl
 RM ?= rm -f
 
 # Common library includes
-# TODO ideally we would want this to be on "not Darwin",
-# rather than shared, but I haven't found a way to achieve this
-# using features supported by both GNU and BSD make
 LDLIBS = -lOpenCL
 
 # OS-specific library includes
 LDLIBS_Darwin = -framework OpenCL
+LDLIBS_Darwin_exclude = -lOpenCL
+
 LDLIBS_Linux = -ldl
 
 LDLIBS += $(LDLIBS_${OS})
 
+# Remove -lOpenCL if OS is Darwin
+LDLIBS := $(LDLIBS:$(LDLIBS_${OS}_exclude)=)
+
 clinfo: clinfo.o
 
 clinfo.o: clinfo.c $(HDR)