Respect user's pkg-config
--- a/Makefile
+++ b/Makefile
@@ -15,8 +15,9 @@ OBJS=gkrellm_radio.o radio.o
 PLUGIN_DIR ?= /usr/local/lib/gkrellm2/plugins
 INSTALL = install -c
 INSTALL_PROGRAM = $(INSTALL) -s
-GTK_CONFIG = pkg-config gtk+-2.0
-CFLAGS := ${CFLAGS} -fPIC -I$(GKRELLMDIR)/include `$(GTK_CONFIG) --cflags`  -DVERSION=\"$(VERSION)\" -Wall
+PKG_CONFIG ?= pkg-config
+GTK_INCLUDE = $(shell ${PKG_CONFIG} gtk+-2.0 --cflags)
+CFLAGS := ${CFLAGS} -fPIC -I$(GKRELLMDIR)/include ${GTK_INCLUDE} -DVERSION=\"$(VERSION)\" -Wall
 
 ifdef WITH_LIRC
 CFLAGS := ${CFLAGS} -DHAVE_LIRC