Packages have to be moved around in the module because they need to be defined
in a particular order : TEXLIVE-SCHEME-BASIC < TEXLIVE-UPDMAP.CFG < any
texlive package making use of TEXLIVE-UPDMAP.CFG.
* gnu/packages/tex.scm (texlive-updmap.cfg): Provide TEXLIVE-SCHEME-BASIC.