Explicitly set to void device flags when GPU is disabled

build/configure.sh

@@ -627,6 +627,9 @@ if [ "xCUBLAS" != "xno" ]; then
     else
 	echo "cuBLAS"
     fi
+else
+    CUBLASFLAGS=""
+    CUBLASLDFLAGS=""
 fi
 # End of cuBLAS checks
 # MAGMA checks
@@ -711,6 +714,9 @@ if [ "x$MAGMA" != "xno" ]; then
     else
 	echo "yes"
     fi
+else
+    MAGMAFLAGS=""
+    MAGMALDFLAGS=""
 fi
 # End of MAGMA checks
 # Offload checks
@@ -755,6 +761,8 @@ EOF
 	echo "no"
 	OFFLOADFLAGS=""
     fi
+else
+    OFFLOADFLAGS=""
 fi
 # End of offload checks
 if [ "x$CXXFLAGS" = "x" ]; then