Compile for mutliple architectures

[KarelPeeters]

First of all thanks for creating this example, it's been working great for me!

Now I'm trying to build for multiple architectures at once, for example 61 and 86. Online I find you should just pass multiple arch and code flags, but when I try that on this example it doesn't work:

cc::Build::new()
    .cuda(true)
    .cudart("shared")
    .flag("-gencode")
    .flag("arch=compute_61,code=sm_61") // GTX 1060 max-q
    .flag("arch=compute_86,code=sm_86") // RTX 3090
    .include("cuda")
    .files(files)
    .compile("libkernels.a")

results in the error

error: failed to run custom build command for `cuda-nn-eval v0.1.0 (C:\Documents\Programming\STTT\AlphaZero\rust\cuda-nn-eval)`
Caused by:
  process didn't exit successfully: `C:\Documents\Programming\STTT\AlphaZero\rust\target\debug\build\cuda-nn-eval-5e3310161a7b7153\build-script-build` (exit code: 1)
  --- stdout
  TARGET = Some("x86_64-pc-windows-msvc")
  OPT_LEVEL = Some("0")
  HOST = Some("x86_64-pc-windows-msvc")
  CXX_x86_64-pc-windows-msvc = None
  CXX_x86_64_pc_windows_msvc = None
  HOST_CXX = None
  CXX = None
  NVCC_x86_64-pc-windows-msvc = None
  NVCC_x86_64_pc_windows_msvc = None
  HOST_NVCC = None
  NVCC = None
  CXXFLAGS_x86_64-pc-windows-msvc = None
  CXXFLAGS_x86_64_pc_windows_msvc = None
  HOST_CXXFLAGS = None
  CXXFLAGS = None
  CRATE_CC_NO_DEFAULTS = None
  CARGO_CFG_TARGET_FEATURE = Some("fxsr,sse,sse2")
  DEBUG = Some("true")
  running: "nvcc" "-ccbin=C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.29.30133\\bin\\HostX64\\x64\\cl.exe" "-Xcompiler" "-nologo" "-Xcompiler" "-MD" "-G" "-Xcompiler" "-Z7" "-Xcompiler" "-Brepro" "-I" "cuda" "-Xcompiler" "-W4" "-gencode" "arch=compute_61,code=sm_61" "arch=compute_86,code=sm_86" "-o" "C:\\Documents\\Programming\\STTT\\AlphaZero\\rust\\target\\debug\\build\\cuda-nn-eval-0c2edb18490f7faf\\out\\cuda/kernels\\fixed_conv.o" "-c" "--device-c" "cuda/kernels\\fixed_conv.cu"
  nvcc fatal   : A single input file is required for a non-link phase when an outputfile is specified
  exit code: 1
  --- stderr
  error occurred: Command "nvcc" "-ccbin=C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.29.30133\\bin\\HostX64\\x64\\cl.exe" "-Xcompiler" "-nologo" "-Xcompiler" "-MD" "-G" "-Xcompiler" "-Z7" "-Xcompiler" "-Brepro" "-I" "cuda" "-Xcompiler" "-W4" "-gencode" "arch=compute_61,code=sm_61" "arch=compute_86,code=sm_86" "-o" "C:\\Documents\\Programming\\STTT\\AlphaZero\\rust\\target\\debug\\build\\cuda-nn-eval-0c2edb18490f7faf\\out\\cuda/kernels\\fixed_conv.o" "-c" "--device-c" "cuda/kernels\\fixed_conv.cu" with args "nvcc" did not execute successfully (status code exit code: 1).
warning: build failed, waiting for other jobs to finish...
error: build failed

when I look for this error online I mostly find mal-formed commandline invocations, but I don't see how having multiple archs would cause that. I also attempted to put everything in a single flag call like this

.flag("arch=compute_61,code=sm_61,arch=compute_86,code=sm_86")

But then I get the nvcc error redefinition of keyword 'arch'.

Is there a way to get this working?