system/gnu-unifont: Updated for version 12.1.02.

Also:

• Remove bashisms when checking FONTFORMATS var
• Print error message if no font format has been selected

Other checks performed:

1. Checked that all download locations point to the same file:

• http://unifoundry.com/pub/unifont/unifont-12.1.02/unifont-12.1.02.tar.gz
• https://ftpmirror.gnu.org/unifont/unifont-12.1.02/unifont-12.1.02.tar.gz
• https://ftp.gnu.org/gnu/unifont/unifont-12.1.02/unifont-12.1.02.tar.gz
• ftp://ftp.gnu.org/gnu/unifont/unifont-12.1.02/unifont-12.1.02.tar.gz

Size: 19740215 bytes

MD5: 39d14d95e86abcf2da2d6c061b71cc9f

SHA256: e812dcf032f0e7a7bb57b98767277701c1d3d0675f5d034f2bf495efa9ed8d8b

2. Verified file signatures.

3. Scanned downloads using ClamAV with latest virus databases.

4. Scanned downloads using VirusTotal:

https://www.virustotal.com/gui/file/e812dcf032f0e7a7bb57b98767277701c1d3d0675f5d034f2bf495efa9ed8d8b/summary