Add documentation about howto build cross toolchain.

git-svn-id: svn+ssh://svn.code.sf.net/p/mingw-w64/code/trunk@28 4407c894-4637-0410-b4f5-ada5f102cad1

mingw-w64-doc/howto-build/mingw-w64-howto-build.txt

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+HowTo build x86_64-pc-mingw32 cross-compiler
+
+Date /		Version /	Author
+2007-07-31  	1.0		Kai Tietz <Kai.Tietz at onevision.com>
+2007-08-20	1.1		Kai Tietz <Kai.Tietz at onevision.com>
+
+This document describes how to build the amd64 mingw32 gcc toolchain as cross-compiler on cygwin and unix shells.
+
+1. Download packages
+The following packages you need to download
+	- binutils 2.17.50 snapshot released after or equal to the 1st of Junly 2007.
+	- gcc version 4.3 snapshort released after or equal to the 1st of Junly 2007.
+	- current mingw-w64-snapshot available on the sourceforge 'mingw-w64'
+
+Now extract these tarballs in an temporary folder. E.g. use ~/w64src. For the tarballs with
+extension .tar.gz or .tgz use the following command to extract : tar -xzf <tarball>'.  For
+tarballs with extension .tar.bz2 or .tbz2 use the command 'tar -xjf <tarball>'.
+There are now three folders within you temporary folder: trunk, binutils, and gcc.
+
+2. Choice of kind of build
+
+You have at least two different choices to build the crosscompiler toolchain:
+ I)  Using standard settings of configure.
+ II) Using --prefix and --with-sysroot configuration
+
+  I assume that <install-root> is for build kind I '/usr/local' and for kind II your specified
+  path.
+
+  Building binutils cross toolchain:
+  Step 1) Enter into the binutils root folder and generate a folder within (e.g.
+	'build'). Than enter into it.
+  Step 2 for I) Type '../configure --target=x86_64-pc-mingw32'
+  Step 2 for II) Type '../configure --target=x86_64-pc-mingw32 --prefix=/vol/m --with-sysroot=/vol/m'.
+	May change the pathes '/vol/m' to pathes you desire.
+  Step 3) Type 'make'
+  Step 4) Type 'make install'
+
+  Now copy the content of the folder 'trunk/mingw-w64-headers/include' into your '<install-root>/x86_64-pc-mingw32/include'
+  folder. If you choose the configuration variant II create in <install-root> a symbolic link named
+  'mingw' pointing to the directory 'x86_64-pc-mingw32'.
+
+  Building the gcc core cross-compiler(s):
+  Step 0) If you have to patch gcc, may do this here. There are some patches necessary, if you want
+  	to cross compile libiberty with early header sets, or if you want to use gfortran. These patches
+  	are available by the 'gcc-patches' mailing list at 'gcc.gnu.org' or by taking a look at mingw.org
+  	or mingw-w64 sites.
+  Step 1) Enter into the gcc root folder and generate a folder within (e.g. 'build'). Than may you
+	apply optional patches to gcc (currently there is a patch file for gcc needed to fix some
+	problems about autoimported variables, libiberty and the fortan compiler).
+  Step 2 for I) Now enter into your created folder (e.g. 'build') and type
+	'../configure --target=x86_64-pc-mingw32'.
+  Step 2 for II) Now enter into your created folder (e.g. 'build') and type
+	'../configure --target=x86_64-pc-mingw32 --prefix=/vol/m --with-sysroot=/vol/m'.
+	May change the pathes '/vol/m' to pathes you desire.
+  Step 3) Type 'make all-gcc'
+  Step 4) Type 'make install-gcc'
+
+  Now the core stuff of gcc is present and we can build the crt itself.
+
+  Building the crt:
+  Step 0) If you are using variant II, may you need to adjust the 'prefix' value in Makefiles.
+  Step 1) Enter into the trunk/mingw-w64-crt root directory.
+  Step 2) Type 'make'
+  Step 3) Copy all generated *.a files out of the 'mklibs' folder into the
+	'<install-root>/x86_64-pc-mingw32/lib' folder.
+  Step 4) Copy out of the root folder to the '<install-root>/x86_64-pc-mingw32/lib' folder the files
+	crt1.o, crt2.o, lib*.a, *.dll, crtbegin.o, crtend.o, dllcrt1.o, dllcrt2.o, binmode.o, txtmode.o,
+	CRT_fp8.o, and the CRT_fp10.o.
+
+  Now you are ready to build the rest of gcc:
+  Step 1) Enter into your generated folder within your gcc root source folder.
+  Step 2) Type 'make'
+  Step 3) Type 'make install'
+