Move node-gyp into optdepends

Description:

node-gyp is used to compile C++ node modules. But the dependency is useless on its own, as it also requires make and gcc to work, which it doesn't depend on.

I.e. it doesn't work on a regular user system (without base-devel installed) anyway. So I think it is better to move it into optdepends.

Additional info:

• package version(s): 10.5.2-1