[CK_BUILDER] Fix two staging-compiler errors in CK builder code (#4598)

This PR fixes two compiler warnings that report as errors with the
latest compiler:

1. In tensor descriptor, the `operator[]` accessor needs a
`[[clang::lifetimebound]]` attribute.
2. In the unit tests for device buffer, there is a test that explicitly
checks for an error on a pointer that went out of scope, so it needs a
to disable `-Wlifetime-safety-permissive` in the test code.

I ran the CK `smoke-builder` tests with the staging compiler to verify.

---------

Co-authored-by: illsilin_amdeng <Illia.Silin@amd.com>

experimental/builder/test/unit_device_buffer.cpp

@@ -48,6 +48,10 @@ TEST(DeviceBuffer, AutoFree)
     const auto size = 12345;
     std::byte* ptr  = nullptr;
 
+    // In this test we are explicitly testing a pointer that is out of scope, so
+    // we have to disable the clang compiler's lifestime safety checks.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wlifetime-safety-permissive"
     {
         auto buffer = ckt::alloc_buffer(size);
         ptr         = buffer.get();
@@ -55,6 +59,7 @@ TEST(DeviceBuffer, AutoFree)
 
     // Trying to use a pointer after freeing should return en error in HIP.
     EXPECT_THAT(hipMemset(ptr, 0xFF, size), HipError(hipErrorInvalidValue));
+#pragma clang diagnostic pop
 
     // Reset internal HIP error state.
     // Otherwise, the error may leak into other tests, triggering anything that