ROHD-2434: Docker falls over a '=' in --build-arg params

Remove the -march=soandso and just pass soandso as build arg
and take care of setting the -march and -mtune parameters in
the Dockerfile.


(cherry picked from commit fc141fee)

Docker/lofar-base/Dockerfile.tmpl

@@ -69,12 +69,12 @@ ENV J=${J}
 ARG CXX_FLAGS="--std=c++11 -W -Wall -Woverloaded-virtual -Wno-unknown-pragmas -D_GLIBCXX_USE_CXX11_ABI=${CXX_ABI} -O3"
 
 # Allow to overwrite the CPU optimisation default setting by specifying
-# --build-arg CPU_OPTIMISATION="-march=native"
-ARG CPU_OPTIMISATION="-march=haswell"
-ENV CPU_OPTIMISATION=${CPU_OPTIMISATION}
+# --build-arg CPU_OPTIMISATION="native"
+ARG CPU_OPTIMISATION="haswell"
+ENV CPU_OPTIMISATION="-march=${CPU_OPTIMISATION} -mtune=${CPU_OPTIMISATION}"
 
 # Combine CXX_FLAGS and CPU_OPTIMISATION
-ENV CXX_FLAGS=${CXXFLAGS} ${CPU_OPTIMISATION}
+ENV CXX_FLAGS="${CXXFLAGS} ${CPU_OPTIMISATION}"
 
 
 #