fix(yarn): set YARN_CACHE_FOLDER if not already (#8180)

Closes #8172

lib/manager/npm/post-update/lerna.ts

@@ -81,6 +81,7 @@ export async function generateLockFiles(
       extraEnv: {
         NPM_CONFIG_CACHE: env.NPM_CONFIG_CACHE,
         npm_config_store: env.npm_config_store,
+        YARN_CACHE_FOLDER: env.YARN_CACHE_FOLDER,
       },
       docker: {
         image: 'renovate/node',

lib/manager/npm/post-update/yarn.ts

@@ -64,6 +64,7 @@ export async function generateLockFile(
     const extraEnv: ExecOptions['extraEnv'] = {
       NPM_CONFIG_CACHE: env.NPM_CONFIG_CACHE,
       npm_config_store: env.npm_config_store,
+      YARN_CACHE_FOLDER: env.YARN_CACHE_FOLDER,
       CI: 'true',
     };