gcc-plugin/src/Makefile.am: add CPPFLAGS for cuda and opencl

gcc-plugin/src/Makefile.am

@@ -25,7 +25,8 @@ AM_YFLAGS = -y
 
 AM_CPPFLAGS =						\
   -I$(top_srcdir)/include				\
-  -I$(GCC_PLUGIN_INCLUDE_DIR) -Wall -DYYERROR_VERBOSE=1
+  -I$(GCC_PLUGIN_INCLUDE_DIR) -Wall -DYYERROR_VERBOSE=1 \
+  $(STARPU_CUDA_CPPFLAGS) $(STARPU_OPENCL_CPPFLAGS)
 
 AM_LDFLAGS = -module --tag="$(GCC_FOR_PLUGIN_LIBTOOL_TAG)"