updated READMEs (compilation instructions) for halo_exchange and dsde samples

halo_exchange/README.md

@@ -69,17 +69,7 @@ Intermediate / Advanced
 
 ## Compiling
 
-In order to build the sample, only a working MPI implementation supporting MPI-3 must be available. To compile, simply run:
-
-    make
-
-If you need to use a MPI wrapper compiler other than `mpicc`, e.g. `mpiicc`, type:
-
-    make MPICC=mpiicc
-
-In order to specify further compilation flags, e.g. `-g`, type:
-
-    make CFLAGS="-g"
+Follow the compilation instructions given in the main directory of the kernel samples directory (`/hpc_kernel_samples/README.md`).
 
 
 ## Running