treewide: Mass replace 'fftwLongDouble}/lib' to refer the 'out' output

pkgs/top-level/python-packages.nix

···
     doCheck = false;
 
     preConfigure = ''
-      export LDFLAGS="-L${pkgs.fftw.out}/lib -L${pkgs.fftwFloat}/lib -L${pkgs.fftwLongDouble}/lib"
+      export LDFLAGS="-L${pkgs.fftw.out}/lib -L${pkgs.fftwFloat}/lib -L${pkgs.fftwLongDouble.out}/lib"
       export CFLAGS="-I${pkgs.fftw}/include -I${pkgs.fftwFloat}/include -I${pkgs.fftwLongDouble}/include"
     '';
     #+ optionalString isDarwin ''