[build] Change check_dependencies.sh to not look for yum if apt-get present.

Author: danpovey

tools/extras/check_dependencies.sh

@@ -122,9 +122,7 @@ if which apt-get >&/dev/null && ! which zypper >/dev/null; then
  echo " sudo apt-get install libatlas3-base"
  printed=true
  fi
-fi
-
-if which yum >&/dev/null; then
+elif which yum >&/dev/null; then
  if [ ! -z "$redhat_packages" ]; then
  echo "$0: we recommend that you run (our best guess):"
  echo " sudo yum install $redhat_packages"
@@ -136,9 +134,7 @@ if which yum >&/dev/null; then
  echo "sudo yum install atlas.x86_64"
  printed=true
  fi
-fi
-
-if which zypper >&/dev/null; then
+elif which zypper >&/dev/null; then
  if [ ! -z "$opensuse_packages" ]; then
  echo "$0: we recommend that you run (our best guess):"
  echo " sudo zypper install $opensuse_packages"