fix: allow overriding RUNNER_TOOL_CACHE from the config file (#178)

- rc.getToolCache(ctx) is used to figure out RUNNER_TOOL_CACHE and  returns RUNNER_TOOL_CACHE if it is found in the runner config, e.g.
  ```yaml
  container:
    env:
	  RUNNER_TOOL_CACHE: /srv/toolcache
  ```
- store the value in the new `toolCache` data member for containers,  in the same way it is done for host
- GetRunnerContext for containers return `toolCache` instead of a  hard coded string
- add integration test

Closes forgejo/runner#184

Reviewed-on: https://code.forgejo.org/forgejo/act/pulls/178
Reviewed-by: Michael Kriese <michael.kriese@gmx.de>
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>

act/runner/runner_test.go

@@ -218,7 +218,8 @@ func (j *TestJobFileInfo) runTest(ctx context.Context, t *testing.T, cfg *Config
 }
 
 type TestConfig struct {
-	LocalRepositories map[string]string `yaml:"local-repositories"`
+	LocalRepositories map[string]string `yaml:"local-repositories,omitempty"`
+	Env               map[string]string `yaml:"env,omitempty"`
 }
 
 func TestRunEvent(t *testing.T) {
@@ -314,6 +315,7 @@ func TestRunEvent(t *testing.T) {
 		{workdir, "set-env-step-env-override", "push", "", platforms, secrets},
 		{workdir, "set-env-new-env-file-per-step", "push", "", platforms, secrets},
 		{workdir, "no-panic-on-invalid-composite-action", "push", "jobs failed due to invalid action", platforms, secrets},
+		{workdir, "tool-cache", "push", "", platforms, secrets},
 
 		// services
 		{workdir, "services", "push", "", platforms, secrets},
@@ -349,6 +351,7 @@ func TestRunEvent(t *testing.T) {
 						}
 					}
 				}
+				config.Env = testConfig.Env
 			}
 
 			table.runTest(ctx, t, config)