here is the error:
Undefined symbol(s) for architecture 'air64':_Z6dnoiseDv2_fPU9MTLdeviceKi', referenced from:_Z9curlNoiseDv2_fhffPU9MTLdeviceKi in nxNoise.air air-lld: error: symbol(s) not found for target 'air64-apple-ios12.0.0' metal: error: air-lld command failed with exit code 1 (use -v to see invocation)
Late but maybe useful for someone: The problem was due to some functions which were declared in header files but not implemented inside .m files. remove that function's declarations solved my problem.
Find the Other Metal Compiler Flags option in the project target Build Settings and add -fcikernel value to that flag in the Metal Compiler and Metal Linker section of Build Settings.
