Issue a warning if patch executable isnt available

[NeroBurner]

Verification

• I searched for similar issues (including closed issues) and found none was relevant.

Introduce the issue

The creation of fonts requires the patch executable to be available in addition to the lv_font_conv executable.

It is available per default on most Linux distributions but not all.

Preferred solution

We should check if it is available and at least issue a warning in CMake if it wasn't found in path

Version

No response