I've built crosstool for ARM on Cygwin, seems to work. Had to set the build directory to some real short path as the thing used to blow up on me with longer directory names. Current crosstool version comes with glibc 2.2.2 . I don't see any reason why you wouldn't be able to build glibc 2.2.5 with it. Unless the compiler couldn't handle it... I haven't tried compiling anything and running it on the Reader yet. The crosstool is able to compile and build ARM executables - testing it is part of the installation.
It's possible Sony was so nice as to distribute the installable binaries for the gcc (cross-compiler) in the Reader's source depository. After all, what do they have to lose? I would try installing those RPMs on RedHat or Fedora, hopefully the binaries would be compatible.