Install and update a fresh msys2 from https://msys2.github.io according to the instructions given there.
NEVER use an installation path for msys2 containing SPACES or other special characters!
Now install the following tools and programs with the help of pacman:
pacman -Sy --noconfirm git svn zip tar autoconf make libtool automake p7zip patch bison gettext-devel wget sshpass texinfo
Now make sure the mingw-w64 toolchain supplied by pacman is NOT installed:
$ gcc -v should show the following error: bash: gcc: command not found
The mingw-builds build script is responsible to download an approbriate toolchain needed for the gcc build process.
./build --mode=gcc-5.3.0 --static-gcc --arch=x86_64 --march-x64='x86-64' --mtune-x64='generic' --buildroot=/tmp/x86_64 --rev=201604 --rt-version=trunk --threads=win32 --exceptions=seh --enable-languages=c,c++,fortran --fetch-only
./build --mode=gcc-5.3.0 --static-gcc --arch=x86_64 --march-x64='x86-64' --mtune-x64='generic' --buildroot=/tmp/x86_64 --rev=201604 --rt-version=trunk --threads=win32 --exceptions=seh --enable-languages=c,c++,fortran --bootstrap --no-multilib --bin-compress
./build --mode=gcc-5.3.0 --static-gcc --arch=i686 --march-x32='pentium4' --mtune-x32='generic' --buildroot=/tmp/i686 --rev=201604 --rt-version=trunk --threads=win32 --exceptions=sjlj --enable-languages=c,c++,fortran --fetch-only
./build --mode=gcc-5.3.0 --static-gcc --arch=i686 --march-x32='pentium4' --mtune-x32='generic' --buildroot=/tmp/i686 --rev=201604 --rt-version=trunk --threads=win32 --exceptions=sjlj --enable-languages=c,c++,fortran --bootstrap --no-multilib --bin-compress
The build process can be accelerated with the flag--jobs=N. The number N given should be the number of cores avaiilabe for the build process.