>>> Unpacking source...
>>> Unpacking BLT2.4z.tar.gz to /var/tmp/portage/dev-tcltk/blt-2.4z-r2/work
 * Applying blt2.4z-install.diff ...
  [ ok ]
 * Applying blt2.4z-64bit.patch ...
  [ ok ]
>>> Source unpacked.
>>> Compiling source in /var/tmp/portage/dev-tcltk/blt-2.4z-r2/work/blt2.4z ...
 * 
 * ERROR: dev-tcltk/blt-2.4z-r2 failed.
 * Call stack:
 * ebuild.sh, line   49:  Called src_compile
 * environment, line 2445:  Called tc-export 'CC' 'CFLAGS'
 * environment, line 2670:  Called die
 * The specific snippet of code:
 * [[ $(type -t tc-get${var}) != "function" ]] && die "tc-export: invalid export variable '${var}'";
 * The die message:
 * tc-export: invalid export variable 'CFLAGS'
 * 
 * If you need support, post the topmost build error, and the call stack if relevant.
 * A complete build log is located at '/var/tmp/portage/dev-tcltk/blt-2.4z-r2/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/dev-tcltk/blt-2.4z-r2/temp/environment'.
 *