[SYCL][E2E] Search for L0 SDK in standalone mode (#18367)

We need this for our internal testing systems which have L0 installed in
a weird path and aren't passing the dir through the LIT vars, and they
shouldn't have to if the relevant envvars are set up as expected.

Also confirming this didn't break the feature detection,
`AtomicRef/device_has_aspect_atomic64_level_zero.cpp` requires
`level_zero_dev_kit` and it's still running:

Lin:
```
2025-05-08T16:36:59.9886240Z Passed Tests (1636):
...
2025-05-08T16:36:59.9910791Z   SYCL :: AtomicRef/device_has_aspect_atomic64_level_zero.cpp
```
Win:
```
2025-05-08T16:32:50.9297718Z Passed Tests (1364):
...
2025-05-08T16:32:50.9305267Z   SYCL :: AtomicRef/device_has_aspect_atomic64_level_zero.cpp
```

Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>

Author: sarnex

sycl/test-e2e/CMakeLists.txt

@@ -14,6 +14,21 @@ if(SYCL_TEST_E2E_STANDALONE)
   if( NOT OpenCL_LIBRARY )
     find_package(OpenCL)
   endif()
+  if(NOT DEFINED LEVEL_ZERO_INCLUDE)
+    find_path(LEVEL_ZERO_PATH level_zero/ze_api.h PATH_SUFFIXES include)
+    if(LEVEL_ZERO_PATH)
+      set(LEVEL_ZERO_INCLUDE "${LEVEL_ZERO_PATH}")
+    endif()
+  endif()
+  if(NOT DEFINED LEVEL_ZERO_LIBS_DIR)
+    find_library(LEVEL_ZERO_LIBS_PATH ze_loader)
+    if(LEVEL_ZERO_LIBS_PATH)
+      # We have the path of the lib, get the containing directory
+      # so we can include it.
+      cmake_path(GET LEVEL_ZERO_LIBS_PATH PARENT_PATH LEVEL_ZERO_LIBS_PATH)
+      set(LEVEL_ZERO_LIBS_DIR "${LEVEL_ZERO_LIBS_PATH}")
+    endif()
+  endif()
 else()
   if( NOT OpenCL_LIBRARY )
     set(OpenCL_LIBRARY "${LLVM_BINARY_DIR}/lib")