errors when trying to build opencv

I am trying to build graphics/opencv. The build fails with the issue below.

This is using gcc 7.5.0

     bash-5.0# gcc --version
     gcc (nb4 20200810) 7.5.0

I am not familiar with this error and google searches show o clear 
answer that I can find.

Any suggested fixes? Possible not to be able to build on this 
architecture? Do I need a different gcc version?


-- Detected processor: powerpc
CMake Warning at cmake/OpenCVDetectCXXCompiler.cmake:107 (message):
   OpenCV: unrecognized target processor configuration
Call Stack (most recent call first):
   CMakeLists.txt:151 (include)


-- Performing Test HAVE_CXX11 (check file: cmake/checks/cxx11.cpp)
-- Performing Test HAVE_CXX11 - Success
-- Performing Test HAVE_CXX_ATOMICS_WITHOUT_LIB (check file: 
cmake/checks/atomic_check.cpp)
-- Performing Test HAVE_CXX_ATOMICS_WITHOUT_LIB - Failed
-- Performing Test HAVE_CXX_ATOMICS_WITH_LIB (check file: 
cmake/checks/atomic_check.cpp)
-- Performing Test HAVE_CXX_ATOMICS_WITH_LIB - Failed
CMake Error at cmake/OpenCVDetectCXXCompiler.cmake:232 (message):
   C++11 compiler must support std::atomic
Call Stack (most recent call first):
   CMakeLists.txt:151 (include)


-- Configuring incomplete, errors occurred!
See also 
"/usr/pkgsrc/graphics/opencv/work/opencv-3.4.9/build/CMakeFiles/CMakeOutput.log".
See also 
"/usr/pkgsrc/graphics/opencv/work/opencv-3.4.9/build/CMakeFiles/CMakeError.log".
*** Error code 1

Stop.
make[1]: stopped in /usr/pkgsrc/graphics/opencv
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/graphics/opencv