Skip building fltk tests

Author: dannye

.github/workflows/main.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Install FLTK
         working-directory: lib/fltk
         run: |
-          cmake -D CMAKE_INSTALL_PREFIX="$(realpath "$PWD/../..")" -D CMAKE_BUILD_TYPE=Release -D FLTK_GRAPHICS_CAIRO=1 -D FLTK_BACKEND_WAYLAND=0 -D FLTK_USE_SYSTEM_LIBPNG=0 -D FLTK_USE_SYSTEM_ZLIB=0 -D FLTK_BUILD_GL=0
+          cmake -D CMAKE_INSTALL_PREFIX="$(realpath "$PWD/../..")" -D CMAKE_BUILD_TYPE=Release -D FLTK_GRAPHICS_CAIRO=1 -D FLTK_BACKEND_WAYLAND=0 -D FLTK_USE_SYSTEM_LIBPNG=0 -D FLTK_USE_SYSTEM_ZLIB=0 -D FLTK_BUILD_GL=0 -D FLTK_BUILD_TEST=0
           make
           make install