Build failures when build directory's pathname has a space

[nyh]

If the build directory's pathname has a space character somewhere, make, scripts/build, and other things they run fail.
The failures are caused by various places where we don't quote pathnames, and made worse where in some places we use the current directory's full pathname (which includes a space) where just a relative pathname would have been possible.

I have a partial fix for this, but it doesn't yet fix all the problems...