fc-cache doesn't work for me because I install in a non-standard place.
In src/fccfg.c I see
#define FONTCONFIG_PATH "/etc/fonts"
Which should probably be somehow changed to refer to the installation prefix.
(I don't have write access in /etc, for starters.)
oops. Thanks for the clue. Had to pull the FONTCONFIG_PATH into the compile
command line to get it expanded correctly.