Support simultaneous ptx and lib building (multiple builds in a single builder)

[guoqingbao]

The current version does not support multiple builder instances and a build instance cannot be used for another build (as also mentioned in #2 ), I have fixed this by making the builder reusable, e.g., building ptx after lib building.

The tested use case:

fn main() {
    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-changed=src/attention.cu");
    println!("cargo:rerun-if-changed=src/copy_blocks_kernel.cu");
    println!("cargo:rerun-if-changed=src/reshape_and_cache_kernel.cu");
    println!("cargo:rerun-if-changed=src/rotary_embedding_kernel.cu");
    let builder = bindgen_cuda::Builder::default();
    println!("cargo:info={builder:?}");
    builder.build_lib("libattention.a");

    let bindings = builder.build_ptx().unwrap();
    bindings.write("src/lib.rs").unwrap();

    println!("cargo:rustc-link-lib=attention"); 
}

[guoqingbao]

The current version does not support multiple builder instances and a build instance cannot be used for another build (as also mentioned in #2 ), I have fixed this by making the builder reusable, e.g., building ptx after lib building.

The tested use case:

fn main() {
    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-changed=src/attention.cu");
    println!("cargo:rerun-if-changed=src/copy_blocks_kernel.cu");
    println!("cargo:rerun-if-changed=src/reshape_and_cache_kernel.cu");
    println!("cargo:rerun-if-changed=src/rotary_embedding_kernel.cu");
    let builder = bindgen_cuda::Builder::default();
    println!("cargo:info={builder:?}");
    builder.build_lib("libattention.a");

    let bindings = builder.build_ptx().unwrap();
    bindings.write("src/lib.rs").unwrap();

    println!("cargo:rustc-link-lib=attention"); 
}

This is a different solution by making the builder reusable instead of using multiple thread pools like #3

[guoqingbao]

@ivarflakstad Hi Ivar, are you able to review this PR? I believe the PR at huggingface/candle#3221 depends on this.

[ivarflakstad]

Suggested change

	version = "0.1.7"
	version = "0.1.5"

We can increment the version in a separate PR when creating a new release.

[ivarflakstad]

Nit: Could create a utility ala get_nvcc_binary and avoid the repetition