Rely on the build configuration of MoarVM more when building the
libraries and executables in rakudo instead of hard coding stuff.

when nmake is called without any argument it tries to execute
the first target. Because nmake knows nothing about .PHONY it sees it as
a normal target and tries to execute that. So we have to put the
.NOTPARALLEL target after the 'all' target.

It seems the NQP config variable 'moar::ldimp' is '' instead of undefined
in rakudo irrespective of it being set to undef in MoarVM/build/setup.pm
where it originates. Thus the check needs to be different.