tests: Add $(top_srcdir)/include to AM_CPPFLAGS.

Fixes this build error with make check.

  CC     collision.o
In file included from ../../../../../src/mesa/main/hash_table.h:34:0,
                 from collision.c:31:
../../../../../src/mesa/main/compiler.h:51:53: fatal error: c99_compat.h: No such file or directory

Signed-off-by: Vinson Lee <vlee@freedesktop.org>

src/mesa/main/tests/hash_table/Makefile.am

@@ -19,6 +19,7 @@
 #  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 AM_CPPFLAGS = \
+	-I$(top_srcdir)/include \
 	-I$(top_srcdir)/src/mesa/main \
 	$(API_DEFINES) $(DEFINES) $(INCLUDE_DIRS)