[Ruby] Cross-Compile Ruby to MIPS platform

I have spent several days to deal with cross-compiling Ruby to MIPS platform and have encountered some problems that bother me for a while. Hopefully I finish all the problems and get work done. Awesome!
For the sake of avoiding these kind of problems, I give the steps and scripts about how to do it:

• Cross Compile OpenSSL

>./config --prefix=$PWD/build --cross-compile-prefix=/home/liudanny/git/NL/toolchains_bin/mipscross/linux/bin/mips64-nlm-linux-elf32btsmip- shared no-asm

We need to check the Makefile with “PLATFORM=mips” and without “-m64”

>make 2>&1 | tee make.out; make install

• Cross Compile zlib

>CC=your_cross_compile_gcc ./configure --prefix=$PWD/build
>make 2>&1 | tee make.out; make install

• Cross Compile Berkeley DB

>CC=your_cross_compile_gcc ../dist/configure --prefix=$PWD/build
>make 2>&1 | tee make.out; make install

• Cross Compile OpenLDAP

>CC=your_cross_compile_gcc LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/liudanny/git/db-6.0.30.NC/build_unix/build/lib:/home/liudanny/git/openssl-1.0.1e/build/ssl/lib LDFLAGS=" -L/home/liudanny/git/db-6.0.30.NC/build_unix/build/lib -L/home/liudanny/git/openssl-1.0.1e/build/ssl/lib" CPPFLAGS=" -I/usr/local/include -I/home/liudanny/git/db-6.0.30.NC/build_unix/build/include -I/home/liudanny/git/openssl-1.0.1e/build/ssl/include" ./configure --prefix=$PWD/mybuild/ --enable-bdb --enable-crypt --host=mips64-nlm-linux --with-yielding_select=yes –with-tls=openssl

Before calling make, commenting out the line in include/portable.h ?
// #define NEED_MEMCMP_REPLACEMENT 1

Modify build/shtool to avoid from stripping error ?
Goto line 980 and find:

if [ “.$opt_s” = .yes ]; then
    if [ “.$opt_t” = .yes ]; then
    echo “strip $dsttmp” 1>&2
    fi
    strip $dsttmp || shtool_exit $?
    fi
 
    Change to the following ?
 
    if [ “.$opt_s” = .yes ]; then
    if [ “.$opt_t” = .yes ]; then
    echo “arm-none-linux-gnueabi-strip $dsttmp” 1>&2
    fi
    arm-none-linux-gnueabi-strip $dsttmp || shtool_exit $?
    fi

>make depend; make; make install

• Cross Compile Ruby 1.8.7

Before cross-compiling Ruby, it must compiles and builds on the server first, then cross-compiling will use its own Ruby to generate the Makefile and other important steps.
Due to Ruby can have many extension libraries, we need to modify Setup.emx to enable the ext libs that we need. And also, copy the needed ruby-ext-libs into ext/ directory In the picture, we add and enable “shadow”, “openssl”, “socket”, “zlib”, and “ldap” ext libs as follows:

>export ac_cv_func_getpgrp_void=yes
>export ac_cv_func_setpgrp_void=yes
>export PATH=/home/liudanny/ruby-1.8.7-p352/build/bin:$PATH
>CC=your_cross_compile_gcc ./configure --prefix=$PWD/build/ --host=mips64-nlm-linux --with-openssl-dir=/home/liudanny/git/openssl-1.0.1e/build --disable-ipv6 --with-openssl-dir=/home/liudanny/git/openssl-1.0.1e/build --with-zlib-dir=/home/liudanny/git/zlib-1.2.5/build --with-ldap-dir=/home/liudanny/git/openldap-2.4.39/mybuild 2>&1 | tee config.out
>make 2>&1 | tee make.out; make install

[Cross-Compile] What's the difference of `./configure` option `--build`, `--host` and `--target`?

When using ./configure especially in cross-compiling purpose, I kind of confuse about the option --build and --host so that the following content is what I found on searching:

some remarks on specifying --host=<host>, --target=<target> and --build=<build
# kindly provided by Keith Marshall:
# 1) build
# this is *always* the platform on which you are running the build
# process; since we are building on Linux, this is unequivocally going to
# specify `linux', with the canonical form being `i686-pc-linux-gnu'.
#
# 2) host
# this is a tricky one: it specifies the platform on which whatever we
# are building is going to be run; for the cross-compiler itself, that's
# also `i686-pc-linux-gnu', but when we get to the stage of building the
# runtime support libraries to go with that cross-compiler, they must
# contain code which will run on the `i686-pc-mingw32' host, so the `host'
# specification should change to this, for the `runtime' and `w32api'
# stages of the build.
#
# 3) target
# this is probably the one which causes the most confusion; it is only
# relevant when building a cross-compiler, and it specifies where the code
# which is built by that cross-compiler itself will ultimately run; it
# should not need to be specified at all, for the `runtime' or `w32api',
# since these are already targetted to `i686-pc-mingw32' by a correct
# `host' specification.

And I found an answer after posting this question.. Still posting it here in case it helps someone else in the future.
http://jingfenghanmax.blogspot.in/2010/09/configure-with-host-target-and-build.html

As per this blog in my case
build will be i686-pc-linux-gnu ( My PC)
host will be mipsel-linux ( The platform I am going to run my code on)
target will be used if I am building a cross-compiling toolchain.
Since I am not building a toolchain, I didnt have to specify target.

 You will have to cross-compile libusb and then copy the library and
header files to a location where your toolchain can locate them. In
the case of CodeSourcery, you can put them in
cs_root/arm-none-linux-gnueabi/lib and
cs_root/arm-none-linux-gnueabi/include for example. You will also need
the library on the target's root filesystem unless you link it
statically, please mind the licencing implications if you do though.