new (for src/library/*/src/Makefile)

git-svn-id: https://svn.r-project.org/R/trunk@5160 00db46b3-68df-0310-9c12-caf00c1e9a41

tools/copy-if-change

@@ -0,0 +1,14 @@
+#!/bin/sh
+#
+# Like cp $1 $2, but if the files are the same, do NOTHING.
+# Status is 0 if $2 is changed, 1 otherwise.
+
+if test -r $2; then
+  if cmp $1 $2 > /dev/null; then
+    echo $2 is unchanged
+  else
+    cp -f $1 $2
+  fi
+else
+  cp $1 $2
+fi