http://bugs.gentoo.org/500692

--- config.mk
+++ config.mk
@@ -7,7 +7,7 @@
 # This is likely to be what you'll want for most systems:
 #
 CC=gcc
-CFLAGS=-O2 -Wall
+CFLAGS+=-Wall
 
 # Set the awk interpreter to use for a script used while compiling.
 # (This should be a `new' awk, such as gawk or mawk.)
--- src/Makefile
+++ src/Makefile
@@ -9,8 +9,8 @@
 # This gets definitions for CC, CFLAGS, BINDIR etc.
 include ../config.mk
 
-CFLAGS+=`pkg-config --cflags gtk+-2.0` `pkg-config --cflags gdk-pixbuf-2.0`
-LDFLAGS+=`pkg-config --libs gtk+-2.0` `pkg-config --libs gdk-pixbuf-2.0`
+CFLAGS+=`pkg-config --cflags gtk+-2.0` `pkg-config --cflags gdk-pixbuf-2.0` `pkg-config --cflags x11`
+LIBS=`pkg-config --libs gtk+-2.0` `pkg-config --libs gdk-pixbuf-2.0` `pkg-config --libs x11` -lm
 
 all: xzgv
 
@@ -23,7 +23,7 @@
 	backend.o
 
 xzgv: $(OBJS)
-	$(CC) $(LDFLAGS) -o xzgv $(OBJS)
+	$(CC) $(LDFLAGS) $(OBJS) $(LIBS) -o xzgv
 
 installdirs:
 	/bin/sh ../mkinstalldirs $(BINDIR)