sourceHighlight: fix build on darwin

Clang has trouble compiling the tests, so re-disable
building them pending an upstream fix.

Changed files
+1 -1
pkgs
tools
text
source-highlight
+1 -1
pkgs/tools/text/source-highlight/default.nix
···
configureFlags = [ "--with-boost=${boost.out}" ];
-
doCheck = true;
+
doCheck = !stdenv.cc.isClang;
enableParallelBuilding = true;
# Upstream uses the same intermediate files in multiple tests, running