see: http://bugs.freedesktop.org/show_bug.cgi?id=13966

diff -Naur Mesa-7.0.2/src/glw/glw.pc.in Mesa-7.0.2-magellan/src/glw/glw.pc.in
--- Mesa-7.0.2/src/glw/glw.pc.in	1970-01-01 01:00:00.000000000 +0100
+++ Mesa-7.0.2-magellan/src/glw/glw.pc.in	2008-02-12 17:39:05.000000000 +0100
@@ -0,0 +1,11 @@
+prefix=@INSTALL_DIR@
+exec_prefix=${prefix}
+libdir=${exec_prefix}/@LIB_DIR@
+includedir=${prefix}/include
+
+Name: glw
+Description: Mesa OpenGL widget library
+Requires: gl
+Version: @VERSION@
+Libs: -L${libdir} -lGLw
+Cflags: -I${includedir}