Compiler: redirect DOTNET_INSTALL_DIR and GOPATH for ARC/DinD topology (#42855)

* fix: redirect DOTNET_INSTALL_DIR and GOPATH for ARC/DinD topology

On ARC/DinD runners, setup-dotnet installs to /usr/share/dotnet by default
which requires root permissions. Similarly, GOPATH defaults to a path that
may not be writable or visible to the DinD daemon.

Extend the existing 'Redirect tool cache for ARC/DinD' step to also set:
- DOTNET_INSTALL_DIR -> ${RUNNER_TEMP}/gh-aw/tool-cache/dotnet
- GOPATH -> ${RUNNER_TEMP}/gh-aw/tool-cache/go

This ensures all runtime setup actions install to daemon-visible, writable paths.

Fixes the 'mkdir: cannot create directory /usr/share/dotnet: Permission denied'
error seen in ARC/DinD canary workflows.

Related: #42807

* test: add assertions for DOTNET_INSTALL_DIR and GOPATH redirects

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: lpcox

pkg/workflow/compiler_yaml_main_job.go

@@ -233,10 +233,12 @@ func (c *Compiler) generateRuntimeAndWorkspaceSetupSteps(yaml *strings.Builder,
 	// This step must run before any runtime setup steps (setup-go, setup-node, etc.) so that
 	// those actions pick up the redirected path when they write into RUNNER_TOOL_CACHE.
 	if isArcDindTopology(data) {
-		yaml.WriteString("      - name: Redirect tool cache for ARC/DinD\n")
+		yaml.WriteString("      - name: Redirect tool cache and install paths for ARC/DinD\n")
 		yaml.WriteString("        run: |\n")
 		yaml.WriteString("          mkdir -p \"${RUNNER_TEMP}/gh-aw/tool-cache\"\n")
 		yaml.WriteString("          echo \"RUNNER_TOOL_CACHE=${RUNNER_TEMP}/gh-aw/tool-cache\" >> \"$GITHUB_ENV\"\n")
+		yaml.WriteString("          echo \"DOTNET_INSTALL_DIR=${RUNNER_TEMP}/gh-aw/tool-cache/dotnet\" >> \"$GITHUB_ENV\"\n")
+		yaml.WriteString("          echo \"GOPATH=${RUNNER_TEMP}/gh-aw/tool-cache/go\" >> \"$GITHUB_ENV\"\n")
 	}
 
 	if needsCheckout || !customStepsContainCheckout {

pkg/workflow/compiler_yaml_main_job_test.go

@@ -748,9 +748,11 @@ func TestGenerateMainJobStepsArcDindRedirectsToolCacheToRunnerTemp(t *testing.T)
 	require.NoError(t, err)
 
 	result := yaml.String()
-	assert.Contains(t, result, "- name: Redirect tool cache for ARC/DinD")
+	assert.Contains(t, result, "- name: Redirect tool cache and install paths for ARC/DinD")
 	assert.Contains(t, result, `mkdir -p "${RUNNER_TEMP}/gh-aw/tool-cache"`)
 	assert.Contains(t, result, `echo "RUNNER_TOOL_CACHE=${RUNNER_TEMP}/gh-aw/tool-cache" >> "$GITHUB_ENV"`)
+	assert.Contains(t, result, `echo "DOTNET_INSTALL_DIR=${RUNNER_TEMP}/gh-aw/tool-cache/dotnet" >> "$GITHUB_ENV"`)
+	assert.Contains(t, result, `echo "GOPATH=${RUNNER_TEMP}/gh-aw/tool-cache/go" >> "$GITHUB_ENV"`)
 	assert.NotContains(t, result, "/tmp/gh-aw/tool-cache")
 }