Disable strictBuiltinIteratorReturn check

'lru-cache' does some things that the typechecker dislikes.
As per the issue isaacs/node-lru-cache#348,
we disable the responsible check.
This unblocks us from using newer typescript versions

Author: fendor

tsconfig.json

@@ -12,7 +12,8 @@
     "noImplicitAny": true,
     "noImplicitReturns": true,
     "noFallthroughCasesInSwitch": true,
-    "strictNullChecks": true
+    "strictNullChecks": true,
+    "strictBuiltinIteratorReturn": false
   },
   "include": ["./src/**/*.ts", "./test/**/*.ts"],
   "exclude": ["node_modules", ".vscode", ".vscode-test"]