fix: static link ggml-blas if openblas feature is enabled

[kaspar030]

... I'm getting undefined symbol: ggml_backend_blas_reg otherwise.

  = note: some arguments are omitted. use `--verbose` to show all linker arguments                                                                             
  = note: mold: error: undefined symbol: ggml_backend_blas_reg                                                                                                 
          >>> referenced by ggml-backend-reg.cpp                                                                                                               
          >>>               /home/kaspar/src.old/own/whisper-http-service/target/debug/deps/libwhisper_rs_sys-4616210e579be9da.rlib(ggml-backend-reg.cpp.o):(gg
ml_backend_registry::ggml_backend_registry())                                                                                                                  
          clang: error: linker command failed with exit code 1 (use -v to see invocation)                                                                      

[tazz4843]

Windows error is spurious and this looks fine to me, thanks for the PR :)