test: fix ngtsc tests in windows (#30146)

This commit fixes the following test target in windows

```
//packages/compiler-cli/test/ngtsc:ngtsc
```

PR Close #30146

.codefresh/codefresh.yml

@@ -20,7 +20,7 @@ steps:
     # Add Bazel CI config
     - copy .codefresh\bazel.rc %ProgramData%\bazel.bazelrc
     # Run tests
-    - yarn bazel test //tools/ts-api-guardian:all //packages/language-service/test //packages/compiler/test //packages/compiler-cli/test:ngc
+    - yarn bazel test //tools/ts-api-guardian:all //packages/language-service/test //packages/compiler/test //packages/compiler-cli/test:ngc //packages/compiler-cli/test/ngtsc:ngtsc
     - yarn test-ivy-aot //packages/animations/test //packages/common/test //packages/forms/test //packages/http/test //packages/platform-browser/test //packages/platform-browser-dynamic/test //packages/router/test
     - yarn bazel test //tools/public_api_guard/...
     - yarn bazel test //packages/compiler-cli/integrationtest:integrationtest //packages/compiler-cli/test/compliance:compliance

packages/compiler-cli/test/ngtsc/env.ts

@@ -29,7 +29,7 @@ function setupFakeCore(support: TestSupport): void {
   const nodeModulesPath = path.join(support.basePath, 'node_modules');
   const angularCoreDirectory = path.join(nodeModulesPath, '@angular/core');
 
-  fs.symlinkSync(fakeNpmPackageDir, angularCoreDirectory, 'dir');
+  fs.symlinkSync(fakeNpmPackageDir, angularCoreDirectory, 'junction');
 }
 
 /**
@@ -121,7 +121,7 @@ export class NgtscTestEnvironment {
     if (this.multiCompileHostExt === null) {
       throw new Error(`Not tracking written files - call enableMultipleCompilations()`);
     }
-    const outDir = path.join(this.support.basePath, 'built');
+    const outDir = path.posix.join(this.support.basePath, 'built');
     const writtenFiles = new Set<string>();
     this.multiCompileHostExt.getFilesWrittenSinceLastFlush().forEach(rawFile => {
       if (rawFile.startsWith(outDir)) {