test: improve unit tests - use virtual file system

- use virtualFileSystem in ULTs, writeDataToFile() does not create file
but instead saves filename. Call to fileExists() checks if file was
previously written

Related-To: NEO-7006

Signed-off-by: Mateusz Hoppe <mateusz.hoppe@intel.com>

shared/test/unit_test/built_ins/sip_tests.cpp

@@ -26,7 +26,12 @@
 
 #include "common/StateSaveAreaHeader.h"
 
+#include <set>
+
 using namespace NEO;
+namespace NEO {
+extern std::set<std::string> virtualFileList;
+}
 
 struct RawBinarySipFixture : public DeviceFixture {
     void setUp() {
@@ -746,4 +751,4 @@ TEST_F(DebugBuiltinSipTest, givenDebuggerWhenInitSipKernelThenDbgSipIsLoadedFrom
     auto sipAllocation = SipKernel::getSipKernel(*pDevice, nullptr).getSipAllocation();
     EXPECT_NE(nullptr, sipAllocation);
     EXPECT_EQ(SipKernelMock::classType, SipClassType::builtins);
-}
+}