Fix the process substitution doesn't work with FONTCONFIG_FILE

Don't address the real filename when a named pipe is given in FONTCONFIG_FILE.
3 jobs for master in 5 minutes and 34 seconds
Status Job ID Name Coverage
  Build
passed #1667825
mingw-build

00:04:21

passed #1667823
shared-build

00:05:34

passed #1667824
static-build

00:04:13