Have Makefile respect user-configured pkg-config
--- a/Makefile
+++ b/Makefile
@@ -1,11 +1,11 @@
 
 VERSION = `cat VERSION`
 PREFIX ?= /usr/local
-GTK_CONFIG = pkg-config gtk+-2.0
+PKG_CONFIG ?= pkg-config
 PLUGIN_DIR ?= $(PREFIX)/lib/gkrellm2/plugins
 GKRELLM_INCLUDE = -I$(PREFIX)/include
-GTK_CFLAGS = `$(GTK_CONFIG) --cflags` 
-GTK_LIB = `$(GTK_CONFIG) --libs`
+GTK_CFLAGS = $(shell ${PKG_CONFIG} gtk+-2.0 --cflags)
+GTK_LIB = $(shell ${PKG_CONFIG} gtk+-2.0 --libs)
 FLAGS = -fPIC $(GTK_CFLAGS) $(GKRELLM_INCLUDE)
 CFLAGS += $(FLAGS)
 CFLAGS += -DVERSION=\"$(VERSION)\"