Cannot install with CMAKE if doc is not (e.g. cannot be) generated

[Alpar Juttner]

For installing lemon using CMAKE, the doc must also be built.

If would be nice if

• the install}} target depended on the {{{html target, so make install would automatically create it
• the html target did nothing but created the html directory when Doxygen or Ghostscript is not available.

[Alpar Juttner]

A much easier and still satisfactory fall back solution can be if cmake simply creates an empty doc/html directory.

So, if (n)make html was run before (n)make install then it will install the doc otherwise it will install just an empty dir.

I even slightly prefer this solution.

[Alpar Juttner]

Replying to alpar:

A much easier and still satisfactory fall back solution can be if cmake simply creates an empty doc/html directory.

So, if (n)make html was run before (n)make install then it will install the doc otherwise it will install just an empty dir.

This solution has gone to both the main and the 1.0 branches, see [8b56605db6a8].