libglnx/libglnx.m4 does not list copy_file_range in AC_CHECK_DECLS, so the HAVE_DECL_COPY_FILE_RANGE preprocessor macro is never defined, and the syscall wrapper detection in libglnx/glnx-missing-syscall.h does not work. This has been “fixed” by tagging the Fedora 27 build into the Fedora 28 buildroot, but this build does not use the correct Fedora build flags.
Thanks, should be fixed by https://github.com/flatpak/flatpak/pull/1389
This bug appears to have been reported against 'rawhide' during the Fedora 28 development cycle. Changing version to '28'.
Confirmed as fixed in flatpak-0.11.3-1.fc28.