travis.yml: Detach build and test steps

travis.yml: Detach build and test steps

Currently build and test commands are a single step in a
Travis's `script` block. In order to see the output
of the tests one needs to scroll down the log to find where
the build messages ended and the limit is not clear. If
they were in different steps then Travis would print the
result build command, which can be easily grep'ed.

So this change is made to detach those commands
to ease the visualization of the output.

Note that all steps on the `script` block is executed regardless
if one previous has failed. To overcome it, let's save the
return code of the build then check whether succeed or failed on
the test step.

Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20191230184327.2800-3-wainersm@redhat.com>