Yea was same for me. It's really not that bad.

   mkdir gcc
   cd gcc
   git clone git://gcc.gnu.org/git/gcc.git src
   mkdir build
   mkdir install
   PREFIX=$(pwd)/install
   cd build
   ../src/configure \
   --enable-host-shared \
   --enable-languages=jit,c++ \
   --disable-bootstrap \
   --enable-checking=release \
   --prefix=$PREFIX \
   --disable-multilib
   nice make -j4 # altering the "4" to however many cores you have

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May need to install some prerequisites listed here https://gcc.gnu.org/install/prerequisites.html (the error message from the configure might not be obvious so better go through the list first, think I needed MPC and MPFR, whatever I found with apt-cache search libmpc and libmpfr worked).

And then configure and make emacs with PATH, LIBRARY_PATH, LD_LIBRARY_PATH including your gcc build (install/bin and install/lib).

[0] taken and modified from https://gcc.gnu.org/onlinedocs/gcc-6.4.0/jit/internals/index...