edksetup.sh: Use bash variable $PWD instead of executing pwd command

This is a (very minor) optimization: `pwd` runs the command (even as a
built-in), whereas $PWD simply evaluates the value of the variable.

ALso, modern scripts should generally use $(...) to run commands,
instead of `...`.

Signed-off-by: Rebecca Cran <[email protected]>
Reviewed-by: Laszlo Ersek <[email protected]>
Reviewed-by: Leif Lindholm <[email protected]>
Message-Id: <[email protected]>

edksetup.sh

@@ -71,7 +71,7 @@ function SetWorkspace()
   #
   # Set $WORKSPACE
   #
-  export WORKSPACE=`pwd`
+  export WORKSPACE=$PWD
   return 0
 }