Use $(shell uname) instead of $(OSTYPE) to detect the MacOS.

diff --git a/support/make/avr/avr.rules b/support/make/avr/avr.rules
index c45ed74794471577aed4d40e41dac9b997ca7cc3..a8c5d025884e010d877fcdd857d93649df303bba 100644 (file)
--- a/support/make/avr/avr.rules
+++ b/support/make/avr/avr.rules
@@ -68,7 +68,7 @@ else
 endif
 
 ifeq ($(PROGRAMMER),avrdude)
-  ifeq ($(findstring darwin, $(OSTYPE)), darwin)
+  ifeq ($(findstring Darwin, $(shell uname)), Darwin)
     AVRDUDE_CONF ?= /opt/local/etc/avrdude.conf
   endif
   AVRDUDE_CONF ?= /etc/avrdude/avrdude.conf