scripts: refine static linking check to better guide the user

The current mechanism to check if static linking is possible, and the mesage
displayed on failure, can be puzzling to the unsuspecting user.

Also, the current implementation is not using the existing infrastructure,
and is thus difficult to enhance with new tests.

So, switch to using the standard CT_DoExecLog infra, and use four tests to
check for the host compiler:
- check we can run it
- check it can build a trivial program
- check it can statically link that program
- check if it statically link with libstdc++

That should cover most of the problems. Hopefully.

(At the same time, fix a typo in a comment)

Signed-off-by: Daniel Price <daniel.price@gmail.com>
[yann.morin.1998@free.fr: split original patch for self-contained changes]
[yann.morin.1998@free.fr: use steps to better see gcc's output]
[yann.morin.1998@free.fr: commit log]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <163f86b5216fc08c672a.1353459722@nipigon.dssd.com>
Patchwork-Id: 200536

 #!@@CT_bash@@

 # What we need:

 #  - the .config file

 # Parse the tools' paths configuration

 . "${CT_LIB_DIR}/paths.sh"

 # We'll need the stdout later, save it

 exec 7>&1

 # Parse the common functions

 . "${CT_LIB_DIR}/scripts/functions"

 # Don't care about any log file

 exec >/dev/null

 rm -f "${tmp_log_file}"

 # Parse the configuration file

 . .config.2

 # Parse architecture and kernel specific functions

 . "${CT_LIB_DIR}/scripts/build/arch/${CT_ARCH}.sh"

 . "${CT_LIB_DIR}/scripts/build/kernel/${CT_KERNEL}.sh"

 # Build CT_TARGET

 CT_DoBuildTargetTuple

 # All this for this single echo... :-( Sigh, I'll have to re-arrange things...

 echo "${CT_TARGET}" >&7