BUILD: make it possible to specify ZLIB path
diff --git a/Makefile b/Makefile
index 02c9291..9641732 100644
--- a/Makefile
+++ b/Makefile
@@ -404,9 +404,12 @@
endif
ifneq ($(USE_ZLIB),)
-OPTIONS_CFLAGS += -DUSE_ZLIB
+# Use ZLIB_INC and ZLIB_LIB to force path to zlib.h and libz.{a,so} if needed.
+ZLIB_INC =
+ZLIB_LIB =
+OPTIONS_CFLAGS += -DUSE_ZLIB $(if $(ZLIB_INC),-I$(ZLIB_INC))
BUILD_OPTIONS += $(call ignore_implicit,USE_ZLIB)
-OPTIONS_LDFLAGS += -lz
+OPTIONS_LDFLAGS += $(if $(ZLIB_LIB),-L$(ZLIB_LIB)) -lz
endif
ifneq ($(USE_POLL),)