Modified ReadMe as the source dir is now PLEXIL_HOME

README

@@ -152,16 +152,20 @@ not recommended.
   mkdir plexil-build
   cd plexil-build
 
-2. Configure the build using CMake.
+2. Configure the build using CMake. Since you changed to the build directory,
+the source (top-level) directory can be indicated with two dots
+after setting up the options. You can set the install directory to the
+current directory using one dot, as shown in the following command.
 
-  cmake "path/to/plexil/src" -DCMAKE_INSTALL_PREFIX="/install/here" ... options ...
+  cmake -DCMAKE_INSTALL_PREFIX=. other_options ..
 
   The example below includes all the optional PLEXIL components as built
   in the previous section, with binaries and libraries installed in the
-  PLEXIL installation directory.  You can omit or change options as
-  desired.
+  PLEXIL installation directory. You can omit or change options as
+  desired. You can use -S to specify the path to the source (top-level
+  or PLEXIL_HOME) directory.
 
-  cmake path/to/plexil/src -DCMAKE_INSTALL_PREFIX="$PLEXIL_HOME" \
+  cmake -S "$PLEXIL_HOME" -DCMAKE_INSTALL_PREFIX="$PLEXIL_HOME" \
     -DGANTT_LISTENER=ON -DSTANDALONE_SIMULATOR=ON -DTEST_EXEC=ON -DUDP_ADAPTER=ON
 
   Please see the CAVEATS file in this directory for advice on CMake options.