Prefer modern-style Bash command substitution in hacking/env-setup

Conflicts:
	hacking/env-setup

hacking/env-setup

@@ -4,16 +4,16 @@
 
 # When run using source as directed, $0 gets set to bash, so we must use $BASH_SOURCE
 if [ -n "$BASH_SOURCE" ] ; then
-    HACKING_DIR=`dirname $BASH_SOURCE`
+    HACKING_DIR=$(dirname $BASH_SOURCE)
 elif [ $(basename $0) = "env-setup" ]; then
-    HACKING_DIR=`dirname $0`
+    HACKING_DIR=$(dirname $0)
 else
     HACKING_DIR="$PWD/hacking"
 fi
 # The below is an alternative to readlink -fn which doesn't exist on OS X
 # Source: http://stackoverflow.com/a/1678636
-FULL_PATH=`python -c "import os; print(os.path.realpath('$HACKING_DIR'))"`
-ANSIBLE_HOME=`dirname "$FULL_PATH"`
+FULL_PATH=$(python -c "import os; print(os.path.realpath('$HACKING_DIR'))")
+ANSIBLE_HOME=$(dirname "$FULL_PATH")
 
 PREFIX_PYTHONPATH="$ANSIBLE_HOME/lib"
 PREFIX_PATH="$ANSIBLE_HOME/bin"