[openvsp] Building fails

[rpxpx]

makepkg fails with following errors:

-- Configuring done (1.8s)
CMake Error at vsp/CMakeLists.txt:39 (TARGET_LINK_LIBRARIES):
Target "vsp" links to:

fltk::gl

but the target was not found. Possible reasons include:

* There is a typo in the target name.
* A find_package call is missing for an IMPORTED target.
* An ALIAS target is missing.

CMake Error at vsp/CMakeLists.txt:57 (TARGET_LINK_LIBRARIES):
Target "apitest_g" links to:

fltk::gl

but the target was not found. Possible reasons include:

* There is a typo in the target name.
* A find_package call is missing for an IMPORTED target.
* An ALIAS target is missing.

CMake Error at /usr/share/cmake/Modules/UseSWIG.cmake:1077 (target_link_libraries):
Target "pyvsp_g" links to:

fltk::gl

but the target was not found. Possible reasons include:

* There is a typo in the target name.
* A find_package call is missing for an IMPORTED target.
* An ALIAS target is missing.

Call Stack (most recent call first):
python_api/CMakeLists.txt:125 (SWIG_LINK_LIBRARIES)