Build failure due to have_cplusplus
I would advise to remove have_cplusplus function for simplicity and to avoid the following build failure:
/home/autobuild/autobuild/instance-12/output-1/host/lib/gcc/aarch64-buildroot-linux-uclibc/10.3.0/../../../../aarch64-buildroot-linux-uclibc/bin/ld: ./.libs/libbayer2rgb3.so: undefined reference to `__bayer2rgb_missing_convert_dumb_implementation'
Full build log: