Move require_distro out from PyPy build definitions

plugins/python-build/share/python-build/pypy-2.3

@@ -1,15 +1,3 @@
-require_distro() {
-  if [[ "$(cat /etc/issue 2>/dev/null || true)" != "$1"* ]]; then
-    { echo
-      colorize 1 "WARNING"
-      echo ": The binary distribution of PyPy is built for $1."
-      echo "installed binary may not run expectedly on other platforms."
-      echo
-    } >&2
-    return 1
-  fi
-}
-
 case "$(pypy_architecture 2>/dev/null || true)" in
 "linux" )
   require_distro "Ubuntu 10.04" || true