Use systemId urn:fontconfig:fonts.dtd to reference the fonts.dtd type defintion

[hegjon]

When packaging font for Fedora Linux, the RPM macro will check if the fontconfig is valid by running the xmllint command.

Before:

Hack/config/fontconfig on  master ❯ xmllint --loaddtd --valid --nonet 45-Hack.conf 45-Hack.conf:2: warning: failed to load external entity "fonts.dtd" <!DOCTYPE fontconfig SYSTEM "fonts.dtd"> ^ 45-Hack.conf:3: validity error : Validation failed: no DTD found ! <fontconfig> ^ <?xml version="1.0"?> <!DOCTYPE fontconfig SYSTEM "fonts.dtd"> <fontconfig> <!-- Declare Hack a monospace font --> <alias> <family>Hack</family> <default><family>monospace</family></default> </alias> <!-- if this file is put in user’s configuration, unset sans-serif family --> <match> <test compare="eq" name="family"> <string>sans-serif</string> </test> <test compare="eq" name="family"> <string>Hack</string> </test> <edit mode="delete" name="family"/> </match> </fontconfig> 

After:

Hack/config/fontconfig on  fontconfig ❯ xmllint --loaddtd --valid --nonet 45-Hack.conf <?xml version="1.0"?> <!DOCTYPE fontconfig SYSTEM "urn:fontconfig:fonts.dtd"> <fontconfig> <!-- Declare Hack a monospace font --> <alias> <family>Hack</family> <default><family>monospace</family></default> </alias> <!-- if this file is put in user’s configuration, unset sans-serif family --> <match> <test compare="eq" name="family"> <string>sans-serif</string> </test> <test compare="eq" name="family"> <string>Hack</string> </test> <edit mode="delete" name="family"/> </match> </fontconfig>