The Monocle build tests warnings as errors, so the x86egl build fails:

$ gradle -PCOMPILE_TARGETS=x86egl
[...]
:graphics:ccX86eglGlassMonocle_x11
/Users/daniel/ws/8u-dev/rt/modules/graphics/src/main/native-glass/monocle/x11/X11.c: In function ‘Java_com_sun_glass_ui_monocle_X_XCreateBitmapFromData’:
/Users/daniel/ws/8u-dev/rt/modules/graphics/src/main/native-glass/monocle/x11/X11.c:269:58: error: unused parameter ‘width’ [-Werror=unused-parameter]
         jlong display, jlong drawable, jobject buf, jint width, jint height) {
                                                          ^
/Users/daniel/ws/8u-dev/rt/modules/graphics/src/main/native-glass/monocle/x11/X11.c:269:70: error: unused parameter ‘height’ [-Werror=unused-parameter]
         jlong display, jlong drawable, jobject buf, jint width, jint height) {
                                                                      ^
/Users/daniel/ws/8u-dev/rt/modules/graphics/src/main/native-glass/monocle/x11/X11.c: In function ‘Java_com_sun_glass_ui_monocle_X_XCreatePixmapCursor’:
/Users/daniel/ws/8u-dev/rt/modules/graphics/src/main/native-glass/monocle/x11/X11.c:278:56: error: unused parameter ‘fg’ [-Werror=unused-parameter]
         jlong display, jlong source, jlong mask, jlong fg, jlong bg,
                                                        ^
/Users/daniel/ws/8u-dev/rt/modules/graphics/src/main/native-glass/monocle/x11/X11.c:278:66: error: unused parameter ‘bg’ [-Werror=unused-parameter]
         jlong display, jlong source, jlong mask, jlong fg, jlong bg,
                                                                  ^
/Users/daniel/ws/8u-dev/rt/modules/graphics/src/main/native-glass/monocle/x11/X11.c:279:14: error: unused parameter ‘x’ [-Werror=unused-parameter]
         jint x, jint y) {
              ^
/Users/daniel/ws/8u-dev/rt/modules/graphics/src/main/native-glass/monocle/x11/X11.c:279:22: error: unused parameter ‘y’ [-Werror=unused-parameter]
         jint x, jint y) {
                      ^
cc1: all warnings being treated as errors