support/testing: allow to indent ccache defconfig fragment

support/testing: allow to indent ccache defconfig fragment

Move the strip out of leading spaces in defconfig fragments from the
BRTest class to the Builder class. It actually postpones the strip out,
consequentially allowing test cases to post-process the defconfig in
their own __init__ before calling the __init__ method from BRTest.

Moving this code to the Builder class also allows any new test class
that inherits from BRTest to reuse the same code even if the new class
overrides the setUp method.

At same time, prepend a newline to the jlevel handling otherwise it
would stop working for defconfig fragments that don't end in a newline.

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Cc: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>