Separate shadow build directory suffixes and build configuration name

Task-number: QTCREATORBUG-11113
Change-Id: Idbf1a52d550a76128bb06ccc65029555fe001078
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>
Reviewed-by: Daniel Teske <daniel.teske@digia.com>