Here is a short experience report for the installation on Ubuntu 12.04.4:
- The URL where GMP can be downloaded has changed since the last
   release. Change
     'wget ftp://ftp.gmplib.org/pub/${GMP}/${GMP}.tar.gz'
   to
     'wget http://ftp.gnu.org/gnu/gmp/${GMP}.tar.gz'
   in install-gcc.sh
- Install gcc-multilib by typing:
    'sudo apt-get install gcc-multilib'
   (as pointed out by 稻草人) before running install-gcc.sh to prevent
   the error "fatal error: bits/predefs.h: No such file or directory"
- Add the option
    --enable-languages=c,c++
   to the call of ./configure in the second-to-last line in
   install-gcc.sh. This makes the installation of gcc more 'lightweight'
   (it does not build the Java,Frotran,Ada,... parts) and reduces the
   risks of compilation problems.
- With new ocaml-compilers you may have difficulties executing
   install-cil.sh
   (error message: "the extension of the output file must be .o or .so")
   This problem can be circumvented by downloading the newest version of
   CREST:
   - svn checkout http://crest.googlecode.com/svn/trunk/ crest-read-only
   - change to the directory 'cil'
   - ./configure
   - make
   - copy the content of the 'cil'-directory into
     $FORENSICTP/cil_crest-1.3.6/
   You can ignore this part if you are not going to use the symbolic
   back-end with concolic execution.