Bazel rules fail to build on MacOS (Darwin x86_64)

[aohren]

Attempting to invoke the Bazel rules for GAPIC generation fails on MacOS. Looks like csharp_compiler_repo.bzl is hardcoded to fetch the Linux x64 version of the dotnet compiler, which obviously won't run on anything except Linux x64?

ERROR: An error occurred during the fetch of repository 'gapic_generator_restore':
   Failed to execute command: `/private/var/tmp/_bazel_aohren/755911223d1a3dde461b23447f5a3cf9/external/csharp_compiler/dotnet_compiler/dotnet restore restore/src/Google.Api.Generator/Google.Api.Generator.csproj --packages=restore/packages --verbosity=quiet`
Exit Code: 126
STDERR: /private/var/tmp/_bazel_aohren/755911223d1a3dde461b23447f5a3cf9/external/csharp_compiler/dotnet_compiler/dotnet: /private/var/tmp/_bazel_aohren/755911223d1a3dde461b23447f5a3cf9/external/csharp_compiler/dotnet_compiler/dotnet: cannot execute binary file

[chrisdunelm]

@aohren You are correct that the rule is currently hardcoded for linux only. This should be fixed.

[jskeet]

Closing as not required.