make fails with: target pattern contains no '%'

[floli]

Hello,

on my Ubuntu 20.04 system, I check out the repo, create a build dir and does cmake .. in it:

$ cmake ..
-- The C compiler identification is GNU 9.4.0
-- The CXX compiler identification is GNU 9.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Warning (dev) at CMakeLists.txt:9 (set):
  implicitly converting 'BOOLEAN' to 'STRING' type.
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Setting build type to 'Debug' as none was specified.
CMake Warning at /usr/share/cmake-3.16/Modules/FindProtobuf.cmake:499 (message):
  Protobuf compiler version doesn't match library version 3.6.1
Call Stack (most recent call first):
  CMakeLists.txt:57 (find_package)


-- Found Protobuf: /usr/lib/x86_64-linux-gnu/libprotobuf.so;-lpthread (found suitable version "3.6.1", minimum required is "2.6.1") 
-- Found Doxygen: /usr/bin/doxygen (found version "1.8.17") found components: doxygen dot 
CMake Warning at CMakeLists.txt:237 (message):
  /proto2cpp.py could not be found.


-- Configuring done
-- Generating done
-- Build files have been written to: /home/lil2lr/workspace/open-simulation-interface/build

which looks good to me. However:

$ make
CMakeFiles/open_simulation_interface_obj.dir/build.make:61: *** target pattern contains no '%'.  Stop.
make[1]: *** [CMakeFiles/Makefile2:135: CMakeFiles/open_simulation_interface_obj.dir/all] Error 2
make: *** [Makefile:130: all] Error 2   

Versions:

cmake version 3.16.3
GNU Make 4.2.1

Thanks!

[ReinhardBiegelIntech]

It's just a guess, as I'm not sure of you skipped some output of the make command. But it looks like there is a problem with protoc not being run? Thus no cpp files are generated and make failes with the mentioned error message. Maybe protoc is provided as a different package? (e.g. in Debian I have the packages libprotobuf-dev and protobuf-compiler installed.