[cairo] Building pdiff fails for builddir != srcdir

[Mathias Hasselmann]

Building pdiff fails for builddir != srcdir. Fix is trivial:

diff --git a/test/pdiff/Makefile.am b/test/pdiff/Makefile.am
index 0a53ce0..89856b8 100644
--- a/test/pdiff/Makefile.am
+++ b/test/pdiff/Makefile.am
@@ -12,5 +12,5 @@ perceptualdiff_SOURCES =      \
        args.h                  \
        perceptualdiff.c
 
-INCLUDES = -I$(top_srcdir)/src $(CAIRO_CFLAGS)
+INCLUDES = -I$(top_srcdir)/src -I$(top_builddir)/src $(CAIRO_CFLAGS)
 LDADD = libpdiff.la $(top_builddir)/src/libcairo.la