go examples don't build with cuda

[glaszig]

• have a system with an nvidia gpu. the server in examples builds with cuda support, no issue.
• build the go examples with GGML_CUDA=1 make example and observe ggml-cuda being built.
• run go-whisper with build_go/go-whisper -model ../../models/ggml-medium.bin samples/jfk.wav and observe that it actually didn't build or link against cuda:

$ build_go/go-whisper -model ../../models/ggml-medium.bin samples/jfk.wav
whisper_init_from_file_with_params_no_state: loading model from '../../models/ggml-medium.bin'
whisper_init_with_params_no_state: use gpu    = 1
whisper_init_with_params_no_state: flash attn = 0
whisper_init_with_params_no_state: gpu_device = 0
whisper_init_with_params_no_state: dtw        = 0
whisper_init_with_params_no_state: devices    = 1
whisper_init_with_params_no_state: backends   = 1
whisper_model_load: loading model
whisper_model_load: n_vocab       = 51865
whisper_model_load: n_audio_ctx   = 1500
whisper_model_load: n_audio_state = 1024
whisper_model_load: n_audio_head  = 16
whisper_model_load: n_audio_layer = 24
whisper_model_load: n_text_ctx    = 448
whisper_model_load: n_text_state  = 1024
whisper_model_load: n_text_head   = 16
whisper_model_load: n_text_layer  = 24
whisper_model_load: n_mels        = 80
whisper_model_load: ftype         = 1
whisper_model_load: qntvr         = 0
whisper_model_load: type          = 4 (medium)
whisper_model_load: adding 1608 extra tokens
whisper_model_load: n_langs       = 99
whisper_model_load:          CPU total size =  1533.14 MB
whisper_model_load: model size    = 1533.14 MB
whisper_backend_init_gpu: no GPU found
whisper_init_state: kv self size  =   50.33 MB
whisper_init_state: kv cross size =  150.99 MB
whisper_init_state: kv pad  size  =    6.29 MB
whisper_init_state: compute buffer (conv)   =   28.57 MB
whisper_init_state: compute buffer (encode) =  170.17 MB
whisper_init_state: compute buffer (cross)  =    7.73 MB
whisper_init_state: compute buffer (decode) =   98.20 MB

system_info: n_threads = 20 / 20 | WHISPER : COREML = 0 | OPENVINO = 0 | CPU : SSE3 = 1 | SSSE3 = 1 | AVX = 1 | AVX_VNNI = 1 | AVX2 = 1 | F16C = 1 | FMA = 1 | BMI2 = 1 | OPENMP = 1 | REPACK = 1 |