/webkit/WebKitWebsiteData/cache is a consistent failure on debug and build bots for WPE, and locally for debug.

This perhaps is a race condition due to some inconsistent results locally versus bots, and debug versus release, as detailed below.

Some initial research:

- - - 
run-wpe tests --release run locally:
 /webkit/WebKitWebsiteData/cache:                                    PASS


run-wpe tests --debug run locally:
 /webkit/WebKitWebsiteData/cache:                                    CRASH
ASSERTION FAILED: m_websiteDataStore
/app/webkit/Source/WebKit/UIProcess/WebProcessProxy.h(187) : 
WebKit::WebsiteDataStore* WebKit::WebProcessProxy::websiteDataStore() const


run-wpe-tests on bots, both --release and --debug:
 /webkit/WebKitWebsiteData/cache:                                    FAIL
ERROR:/app/webkit/Tools/TestWebKitAPI/Tests/WebKitGLib/TestWebsiteData.cpp:432:
void testWebsiteDataCache(WebsiteDataTest*, gconstpointer): 'dataList' should be nullptr