This bashism is not supported by busybox ash. Busybox interprets this as
a single file name and due to the -f flag being passed this does not
result in an error.
This regression was introduced in 010d7fa4.
Without mupdf constantly outputs:
warning: jbig2dec error: incompatible jbig2dec
header (0.17) and library (0.18) versions
RDF library for accessing plugin metadata in the LADSPA plugin system