The E dep for sandbox gadget is not required, don't make it so.

data/desktop/meson.build

@@ -12,9 +12,10 @@ if host_os == 'linux'
                 host_os = 'linux-gnu'
         endif
 endif
-dep_e = dependency('enlightenment')
-release = dep_e.get_pkgconfig_variable('release')
-module_arch = '@0@-@1@-@2@'.format(host_os, host_machine.cpu_family(), release)
-dir_gadgets = join_paths([dir_lib, 'enlightenment/gadgets', module_arch])
-install_data('slideshow.desktop',
-        install_dir: join_paths([dir_gadgets, 'slideshow']))
+if (build_gadget == true)
+        release = depe.get_pkgconfig_variable('release')
+        module_arch = '@0@-@1@-@2@'.format(host_os, host_machine.cpu_family(), release)
+        dir_gadgets = join_paths([dir_lib, 'enlightenment/gadgets', module_arch])
+        install_data('slideshow.desktop',
+                install_dir: join_paths([dir_gadgets, 'slideshow']))
+endif

meson.build

@@ -11,6 +11,8 @@ proj     = meson.project_name()
 ver      = meson.project_version()
 cfg      = configuration_data()
 
+build_gadget = false
+
 ##### dependencies
 efl_version = '>= 1.19.0'
 elm  = dependency('elementary', required: true,  version: efl_version)
@@ -67,6 +69,7 @@ if exif.found() == true
     cfg.set       ('HAVE_LIBEXIF'        , 1)
 endif
 if depe.found() == true
+    build_gadget = true
     cfg.set       ('HAVE_E'              , 1)
 endif
 ##### translations