installer: reapply b21c8e0b, honor --without-npm
installer: reapply b21c8e0b, honor --without-npm

This bug was already fixed in the v0.8 branch but git skips the patch when
merging v0.8 into master. Reapply it manually.

Fixes #3961.

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node