Use containerization 0.7.1. (#606)

- Makes available the proxy utility from containerization#288.

## Type of Change
- [ ] Bug fix
- [x] New feature  
- [ ] Breaking change
- [ ] Documentation update

## Motivation and Context
The proxy utility allows forward progress on #533.

## Testing
- [x] Tested locally
- [ ] Added/updated tests
- [ ] Added/updated docs

Author: jglogan

Package.resolved

@@ -23,7 +23,7 @@ import PackageDescription
 let releaseVersion = ProcessInfo.processInfo.environment["RELEASE_VERSION"] ?? "0.0.0"
 let gitCommit = ProcessInfo.processInfo.environment["GIT_COMMIT"] ?? "unspecified"
 let builderShimVersion = "0.6.0"
-let scVersion = "0.7.0"
+let scVersion = "0.7.1"
 
 let package = Package(
     name: "container",