Update Makefile for MacOS.

Makefile

@@ -3,26 +3,25 @@ CC              = gcc
 VERSION         = $(shell git describe --tags --abbrev=0)
 GITCOUNT        = $(shell git rev-list HEAD --count)
 UNAME           = $(shell uname)
-CFLAGS          = -g -O -Wall -Werror -DVERSION='"$(VERSION).$(GITCOUNT)"'
-LDFLAGS         = -g
 
 OBJS            = main.o util.o radio.o dfu-libusb.o uv380.o md380.o rd5r.o gd77.o hid.o serial.o d868uv.o
-LIBS            =
+LIBS            = $(shell pkg-config --libs --static libusb-1.0)
+LDFLAGS         = -g
+CFLAGS          = -g -O -Wall -Werror -DVERSION='"$(VERSION).$(GITCOUNT)"' \
+                  $(shell pkg-config --cflags libusb-1.0)
 
 #
 # Linux
 #
 # To install required libraries, use:
-#   sudo apt install libusb-1.0-0-dev libudev-dev
+#   sudo apt-get install pkg-config libusb-1.0-0-dev libudev-dev
 #
 ifeq ($(UNAME),Linux)
     OBJS        += hid-libusb.o
-    CFLAGS      += $(shell pkg-config --cflags libusb-1.0)
-    LIBS        += $(shell pkg-config --libs --static libusb-1.0)
 
+    # Link libusb statically, when possible
     LIBUSB      = /usr/lib/x86_64-linux-gnu/libusb-1.0.a
     ifeq ($(wildcard $(LIBUSB)),$(LIBUSB))
-        # Link libusb statically, when possible
         LIBS    = $(LIBUSB) -lpthread -ludev
     endif
 endif
@@ -30,6 +29,9 @@ endif
 #
 # Mac OS X
 #
+# To install required libraries, use:
+#   brew install pkg-config libusb
+#
 ifeq ($(UNAME),Darwin)
     OBJS        += hid-macos.o
     LIBS        += -framework IOKit -framework CoreFoundation