If you clone the openjfx build as follows:

$ hg clone http://hg.openjdk.java.net/openjfx/2.2/master
$ cd master
$ hg clone http://hg.openjdk.java.net/openjfx/2.2/master/rt
$ export JFXRT_HOME=/path/to/downloaded/jfx/rt/lib
$ ant

-------------------------------
check-binary-css:

javafx-ui-controls-common.-pre-init:
    [mkdir] Created dir: C:\Users\kcr\javafx\openjfx\2.2\master-build\jfx\rt\javafx-ui-controls\build\classes\com\sun\javafx\scene\control\skin\caspian
     [java] Exception in thread "main" java.lang.NoClassDefFoundError: com/sun/scenario/ToolkitAccessor
     [java] at com.sun.javafx.Logging.getCSSLogger(Unknown Source)
     [java] at com.sun.javafx.css.parser.CSSParser.<clinit>(Unknown Source)
     [java] at com.sun.javafx.css.parser.Css2Bin.convertToBinary(Unknown Source)
     [java] at com.sun.javafx.css.parser.Css2Bin.main(Unknown Source)
     [java] Caused by: java.lang.ClassNotFoundException: com.sun.scenario.ToolkitAccessor
     [java] at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
     [java] at java.security.AccessController.doPrivileged(Native Method)
     [java] at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
     [java] at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
     [java] at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
     [java] at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
     [java] ... 4 more

BUILD FAILED
C:\Users\kcr\javafx\openjfx\2.2\master-build\jfx\rt\build.xml:65: The following error occurred while executing this line:
C:\Users\kcr\javafx\openjfx\2.2\master-build\jfx\rt\javafx-ui-controls\build-common.xml:12: Java returned: 1