[mb2] Use _smp_mflags instead of the jobs macro for multicore builds
[mb2] Clean up debug

Signed-off-by: David Greaves <david.greaves@jollamobile.com>
[mb2] Ensure key present

Signed-off-by: David Greaves <david.greaves@jollamobile.com>
[mb2] Improve XML handling to better support multiple devices

Signed-off-by: David Greaves <david.greaves@jollamobile.com>
[sb2] Accelerate more binaries in sdk-build(+pp) modes

Accelerate the following binaries:

Always, if found in tools root:
/usr/bin/{localedef, ccache, qtchooser, cpio, zip, xz, cmake},
/usr/lib/qt4/bin/{qmake, moc, uic},
/usr/lib/qt5/bin/{qmake, moc, uic}

Conditionally if also found in target root:
/usr/bin/doxygen

Signed-off-by: Juha Kallioinen <juha.kallioinen@jollamobile.com>