It's working.

export XDG_DATA_DIRS="$HOME/.guix-profile/share${XDG_DATA_DIRS:+:}$XDG_DATA_DIRS"

This solution is effective for LFS too. Thank you.

2019年1月8日(火) 3:10 Andreas Enge <andreas@enge.fr>:
Hello,

I am having the same problem with icecat-60.3.0-gnu1 from commit c71bbfc,
but with a different font:

...
(/gnu/store/iin8fiv8bc11r7wnxck57rhfb74v7d57-icecat-60.3.0-gnu1/lib/icecat/.icecat-real:15119): Pango-WARNING **: 18:04:29.559: failed to create cairo scaled font, expect ugly output. the offending font is 'Nimbus Sans L 10'
(/gnu/store/iin8fiv8bc11r7wnxck57rhfb74v7d57-icecat-60.3.0-gnu1/lib/icecat/.icecat-real:15119): Pango-WARNING **: 18:04:29.560: font_face status is: file not found
(/gnu/store/iin8fiv8bc11r7wnxck57rhfb74v7d57-icecat-60.3.0-gnu1/lib/icecat/.icecat-real:15119): Pango-WARNING **: 18:04:29.560: scaled_font status is: file not found
(/gnu/store/iin8fiv8bc11r7wnxck57rhfb74v7d57-icecat-60.3.0-gnu1/lib/icecat/.icecat-real:15119): Pango-WARNING **: 18:04:29.560: shaping failure, expect ugly output. shape-engine='PangoFcShapeEngine', font='Nimbus Sans L 10', text='●'
(/gnu/store/iin8fiv8bc11r7wnxck57rhfb74v7d57-icecat-60.3.0-gnu1/lib/icecat/.icecat-real:15119): Pango-WARNING **: 18:04:29.562: failed to create cairo scaled font, expect ugly output. the offending font is 'Nimbus Sans L 11.666015625'
(/gnu/store/iin8fiv8bc11r7wnxck57rhfb74v7d57-icecat-60.3.0-gnu1/lib/icecat/.icecat-real:15119): Pango-WARNING **: 18:04:29.562: font_face status is: file not found
(/gnu/store/iin8fiv8bc11r7wnxck57rhfb74v7d57-icecat-60.3.0-gnu1/lib/icecat/.icecat-real:15119): Pango-WARNING **: 18:04:29.562: scaled_font status is: file not found
(/gnu/store/iin8fiv8bc11r7wnxck57rhfb74v7d57-icecat-60.3.0-gnu1/lib/icecat/.icecat-real:15119): Pango-WARNING **: 18:04:29.562: shaping failure, expect ugly output. shape-engine='PangoFcShapeEngine', font='Nimbus Sans L 11.666015625', text='Zwölf Boxkämpfer jagen Viktor quer über den großen Sylter Deich.'
...

This is Guix on top of Debian. My previous version was 52.6.0, so I cannot
say when things broke... I kept the old version since I wanted to use the
Requestpolicy extension.

The problem persists after deleting $HOME/.cache/fontconfig and running
   fc-cache -f -v

It also persists when removing $HOME/.mozilla (which surprisingly is not
recreated when running icecat).

Andreas