I'm following this tutorial: https://youtu.be/rVCt5E1CvZU?t=7m40s
But when I enter the build folder and enter 'ant' (as shown in the video above) I get the following error:
[cc] 1 total files to be compiled.
[cc] In file included from /home/pierce/Downloads/leJOS_NXJ_0.9.1beta-3/build/libnxt/main_jlibnxt.c:30:0:
[cc] /home/pierce/Downloads/leJOS_NXJ_0.9.1beta-3/build/libnxt/jlibnxt.h:2:17: fatal error: jni.h: No such file or directory
[cc] #include <jni.h>
[cc] compilation terminated.
/home/pierce/Downloads/leJOS_NXJ_0.9.1beta-3/build/build.xml:87: The following error occurred while executing this line:
/home/pierce/Downloads/leJOS_NXJ_0.9.1beta-3/build/libnxt/build.xml:39: gcc failed with return code 1
Total time: 0 seconds
I've been looking for a solution for a couple of days but haven't found anyone with the same issue, so any help would be appreciated.