[java] What's the location of the JavaFX runtime JAR file, jfxrt.jar, on Linux?

I'm trying to run some JavaFX code with Eclipse Kepler, with e(fx)clipse plugin installed, on a Linux machine, using:

java version "1.7.0_21"
OpenJDK Runtime Environment (IcedTea 2.3.9) (7u21-2.3.9-5)
OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)

My understanding is that although JavaFX has been included with the standard JDK since version JDK 7u6, the JavaFX runtime JAR file, jfxrt.jar, was left off of the Java runtime path on purpose until further testing between JavaFX and rest of the java infrastructure has been completed. For this reason you must manually add it to the project build path libraries when we create a new Java project.

I've been looking for that jar in both the following directories without success:

/usr/lib/jvm/java-7-openjdk-common/jre/lib/
/usr/lib/jvm/java-7-openjdk-amd64/lib

Where else should I look for it?

Mine were located here on Ubuntu 18.04 when I installed JavaFX using apt install openjfx (as noted already by @jewelsea above)

/usr/share/java/openjfx/jre/lib/ext/jfxrt.jar
/usr/lib/jvm/java-8-openjdk-amd64/jre/lib/ext/jfxrt.jar

The location of jfxrt.jar in JDK 1.8 (Windows) is:

C:\Program Files\Java\jdk1.8.0_05\jre\lib\ext\jfxrt.jar

On Ubuntu with OpenJDK, it installed in /usr/lib/jvm/default-java/jre/lib/ext/jfxrt.jar (technically its a symlink to /usr/share/java/openjfx/jre/lib/ext/jfxrt.jar, but it is probably better to use the default-java link)