gretl: disable install parallelism

Without the change parallel installs fail as:

cp: cannot stat '...-gretl-2022c/share/gretl/data/plotbars': Not a directory
make[1]: *** [Makefile:73: install_datafiles] Error 1

+4
+4
pkgs/applications/science/math/gretl/default.nix
··· 28 nativeBuildInputs = [ pkg-config ]; 29 30 enableParallelBuilding = true; 31 32 meta = with lib; { 33 description = "A software package for econometric analysis";
··· 28 nativeBuildInputs = [ pkg-config ]; 29 30 enableParallelBuilding = true; 31 + # Missing install depends: 32 + # cp: cannot stat '...-gretl-2022c/share/gretl/data/plotbars': Not a directory 33 + # make[1]: *** [Makefile:73: install_datafiles] Error 1 34 + enableParallelInstalling = false; 35 36 meta = with lib; { 37 description = "A software package for econometric analysis";