* gnu/packages/gnome.scm
(json-glib)[arguments]<#:configue-flags>: Set gtk_doc=disables when
cross-compiling.
(json-glib)[arguments]<#:phases>{move-docs}: Don't run when cross-compiling
...
(json-glib)[arguments]<#:phases>{stub-docs}: ... instead, create an empty
directory where the documentation would be.