The scripts provided by the MinGW-W64 project[1] are designed
for building the dual-target(i686/x86_64) MinGW-W64 compiler for i686/x86_64 hosts.

The scripts are distributed under the 'BSD 3' license[2].

In order to use the scripts provided by the MinGW-W64 project it is needed:

1. Windows-64bit or Linux + Wine-64bit

2. Install MSYS2:
  http://sourceforge.net/projects/msys2/

3. Get the scripts into '<msys root>/home/<user>/mingw-w64-builds':
  "cd && git clone <paste correct url>"

4. In the MSYS file structure delete the '/MinGW' directory.

5. Delete the paths pointing to any preinstalled MinGW from the 'PATH'
  environment variable.

6. Go into the MinGW-builds root directory.
  "cd && cd mingw-w64-builds"

7. Options:
  '--mode=[gcc|python|clang]-version' - what package to build with version.
  '--arch=<i686|x86_64>'              - build architecture.
  '--buildroot=<path>'                - using '<path>' as build directory.
                                        By default used MSYS user home directory.
  '--fetch-only'                      - only download all the sources without start building.
  '--update-sources'                  - try to update sources from repositories before build.
  '--exceptions=<model>'              - exceptions handling model.
                                        Available: dwarf, seh(gcc>=4.8.0 only), sjlj.
  '--use-lto'                         - building with using LTO.
  '--no-strip'                        - don't strip executables during install.
  '--no-multilib'                     - build GCC without multilib support (default for DWARF and SEH exception models).
  '--static-gcc'                      - build static GCC.
  '--dyn-deps'                        - build GCC with dynamically dependencies.
  '--rt-version=<v3|v4>'              - version of mingw-w64 runtime to build.
  '--rev=N'                           - number of the build revision.
  '--with-testsuite'                  - run testsuite for packages that contain flags for it.
  '--threads=<posix|win32>'           - used threads model.
  '--enable-languages=<langs>'        - comma separated list(without spaces) of gcc supported languages.
                                        available languages: ada,c,c++,fortran,objc,obj-c++
  For more options run: "./build --help"

8. Run:
  "./build --mode=gcc-4.8.1 --arch=i686" for building i686-MinGW-w64
  "./build --mode=gcc-4.8.1 --arch=x86_64" for building x86_64-MinGW-w64
  "./build --mode=gcc-4.8.1 --arch=x86_64 --preload" for preload sources and building x86_64-MinGW-w64
  "./build --mode=gcc-4.8.1 --arch=i686 --exceptions=dwarf" for building i686-MinGW-w64 with DWARF exception handling

For example, during the process of building of the i686-gcc-4.7.2 will
  be created the following directories:
  <buildroot>/i686-4.7.2-release-posix-sjlj-rev1/build
  <buildroot>/i686-4.7.2-release-posix-sjlj-rev1/libs
  <buildroot>/i686-4.7.2-release-posix-sjlj-rev1/logs
  <buildroot>/i686-4.7.2-release-posix-sjlj-rev1/prefix

For x86_64:
  <buildroot>/x86_64-4.7.2-release-posix-sjlj-rev1/build
  <buildroot>/x86_64-4.7.2-release-posix-sjlj-rev1/libs
  <buildroot>/x86_64-4.7.2-release-posix-sjlj-rev1/logs
  <buildroot>/x86_64-4.7.2-release-posix-sjlj-rev1/prefix

And the sources directory:
  <buildroot>/mingw-sources


The archives with the built MinGW will be created in '<buildroot>/archives/'

At the moment, successfully building the following versions:
  gcc-4.6.2
  gcc-4.6.3
  gcc-4.6.4
  gcc-4.7.0
  gcc-4.7.1
  gcc-4.7.2
  gcc-4.7.3
  gcc-4.8.0
  gcc-4.8.1
  gcc-4.8.2
  gcc-4_6-branch (currently 4.6.5 prerelease)
  gcc-4_7-branch (currently 4.7.4 prerelease)
  gcc-4_8-branch (currently 4.8.3 prerelease)
  gcc-trunk (currently 4.9.0 snapshot)

Builds also contains patches for building Python 2.7.3, 2.7.4, 2.7.5 and 3.3.0 versions for support gdb pretty printers.
Big thanks for these patches to:
  2010-2012 Roumen Petrov, Руслан Ижбулатов
  2012 Ray Donnelly
 
[1] http://sourceforge.net/projects/mingw-w64/
[2] http://www.opensource.org/licenses/BSD-3-Clause