contrib: fix gcc test suite on system without echo -e

Fix the use of quotes in contrib/gcc-test-suite/Makefile to solve the
problem where board.exp is incorrectly generated on some build systems
where 'echo -e' is not handled correctly.

Signed-off-by: Andy Gibbs <andyg1001@hotmail.co.uk>
[Yann E. MORIN: fix space damage, pretty-up the stuff]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 hg