Respect user's pkg-config, don't call gcc directly
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,9 @@
 PKGNAME = gkrellweather
 VERSION = 2.0.8
-CFLAGS = -O2 -std=gnu99 -Wall -fPIC `pkg-config gtk+-2.0 --cflags`
-LIBS = `pkg-config gtk+-2.0 --libs`
+PKG_CONFIG ?= pkg-config
+GTK_INCLUDE = $(shell ${PKG_CONFIG} gtk+-2.0 --cflags)
+CFLAGS = -std=gnu99 -fPIC $(GTK_INCLUDE)
+LIBS =  $(shell ${PKG_CONFIG} gtk+-2.0 --libs)
 LFLAGS = -shared
 PREFIX = /usr/local
 
@@ -16,7 +18,7 @@ endif
 CFLAGS += -DPACKAGE="\"$(PKGNAME)\""
 export PKGNAME LOCALEDIR
 
-CC = gcc
+CC = $(CC)
 
 OBJS = gkrellweather.o