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

 # Test suite config options

 if EXPERIMENTAL

 menu "Test suite"

 config TEST_SUITE

     bool

 config TEST_SUITE_GCC

     bool

     prompt "GCC test suite"

     depends on EXPERIMENTAL

     select TEST_SUITE

     help

       Select this option to install the GCC test suite in $CT_PREFIX_DIR/test_suite.

       The GCC test suite includes a collection of various toolchain tests for GCC -

       it utilizes the DejaGnu test framework.

       For some tests a network enabled target with ssh server is required.

       A helper Makefile is provided for running the tests - please see the included

       README for information on how to run the test suite.

 endmenu

 endif