Address review comments

Author: vladimirlaz

sycl/test/Unit/lit.cfg.py

@@ -73,5 +73,7 @@ def find_shlibpath_var():
     lit_config.warning("unable to inject shared library path on '{}'"
                        .format(platform.system()))
 
+config.environment['SYCL_CACHE_DIR'] = config.llvm_obj_root + "/sycl_cache"
 config.environment['SYCL_DEVICE_FILTER'] = lit_config.params.get('SYCL_PLUGIN', "opencl") + ",host"
 lit_config.note("Backend: {}".format(config.environment['SYCL_DEVICE_FILTER']))
+lit_config.note("SYCL cache directory: {}".format(config.environment['SYCL_CACHE_DIR']))

sycl/unittests/kernel-and-program/PersistentDeviceCodeCache.cpp

@@ -81,6 +81,10 @@ class PersistenDeviceCodeCache : public ::testing::Test {
     return _putenv_s(name, value);
   }
 #endif
+  virtual void SetUp() {
+    assert(getenv("SYCL_CACHE_DIR") && "Please set SYCL_CACHE_DIR environment "
+                                       "variable pointing to cache location.");
+  }
 
   PersistenDeviceCodeCache() : Plt{default_selector()} {
 
@@ -91,8 +95,6 @@ class PersistenDeviceCodeCache : public ::testing::Test {
       return;
     }
 
-    set_env("SYCL_CACHE_DIR", ".");
-
     Mock = std::make_unique<unittest::PiMock>(Plt);
     Dev = Plt.get_devices()[0];
     Mock->redefine<detail::PiApiKind::piProgramGetInfo>(