build: fix out of tree builds.

Author: Christian Hergert

examples/Makefile.am

@@ -4,7 +4,10 @@ EXAMPLE_LDADD = libmongoc-1.0.la
 if EXPLICIT_LIBS
 EXAMPLE_LDADD += $(BSON_LIBS)
 endif
-EXAMPLE_CFLAGS = -I$(top_srcdir)/src/mongoc $(BSON_CFLAGS)
+EXAMPLE_CFLAGS = \
+	-I$(top_srcdir)/src/mongoc \
+	-I$(top_builddir)/src/mongoc \
+	$(BSON_CFLAGS)
 
 noinst_PROGRAMS += example-gridfs
 example_gridfs_SOURCES = examples/example-gridfs.c