Add conformance for projectRoot pcl function

I also added a cache clear before testing to purge any old versions with
the same version number if present, as well as some docs describing this
issue which cost me an hour.

Part of #18565
Blocked by #18595

Changes required to get project root in dotnet and have conformance
tests pass.

Author: brandonpollack23

CHANGELOG_PENDING.md

@@ -0,0 +1 @@
+* Add conformance for rootDirectory to the sdk

CONTRIBUTING.md

@@ -17,6 +17,29 @@ $ changie new
 ✔ GitHub Pull Request … 123
 ```
 
+## Running conformance tests
+
+When running conformance tests, nuget package caches can sometimes cause updates do the SDK to fail,
+in this case you can fix it by deleting the pulumi package from your cache like so:
+
+```shell
+rm -rf ~/.nuget/packages/pulumi/
+```
+
+or clearing the entire cache with
+
+```shell
+dotnet nuget locals --clear all
+```
+
+or simply
+
+```shell
+make clear_nuget_cache
+```
+
+This is done automatically before running `make conformance_tests`
+
 ## Release
 
 To release a new version use `changie` to update the changelog file, open a PR for that change. Once that PR merges it will trigger a release workflow.

Makefile

@@ -15,10 +15,13 @@ build::
 changelog::
 	changie new
 
+clear_nuget_cache::
+	dotnet nuget locals --clear all
+
 test_integration:: build
 	cd integration_tests && gotestsum -- --parallel 1 --timeout 60m ./...
 
-test_conformance:: build
+test_conformance:: clear_nuget_cache build
 	cd pulumi-language-dotnet && gotestsum -- --timeout 60m ./...
 
 # Relative paths to directories with go.mod files that should be linted.

pulumi-language-dotnet/main.go

@@ -814,6 +814,7 @@ func (host *dotnetLanguageHost) constructEnv(req *pulumirpc.RunRequest, config,
 	maybeAppendEnv("engine", host.engineAddress)
 	maybeAppendEnv("organization", req.GetOrganization())
 	maybeAppendEnv("project", req.GetProject())
+	maybeAppendEnv("root_directory", req.GetInfo().RootDirectory)
 	maybeAppendEnv("stack", req.GetStack())
 	maybeAppendEnv("pwd", req.GetPwd())
 	maybeAppendEnv("dry_run", strconv.FormatBool(req.GetDryRun()))