[SYCL] Allow ESIMD backend only when explicitly set by ONEAPI_DEVICE_SELECTOR (#7336)

ONEAPI_DEVICE_SELECTOR would previously implicitly allow ESIMD backends
. This isn't desired behavior; desired behavior is to only allow ESIMD
backend only when explicitly specified by ONEAPI_DEVICE_SELECTOR.
Fix suggested by @lbushi25 

Signed-off-by: Rauf, Rana <[email protected]>

Author: raaiq1

sycl/source/detail/device_filter.cpp

@@ -237,10 +237,13 @@ ods_target_list::ods_target_list(const std::string &envStr) {
 // 1. Filter backend is '*' which means ANY backend.
 // 2. Filter backend match exactly with the given 'Backend'
 bool ods_target_list::backendCompatible(backend Backend) {
+
+  bool isESIMD = Backend == backend::ext_intel_esimd_emulator;
   return std::any_of(
       TargetList.begin(), TargetList.end(), [&](ods_target &Target) {
         backend TargetBackend = Target.Backend.value_or(backend::all);
-        return (TargetBackend == Backend) || (TargetBackend == backend::all);
+        return (TargetBackend == Backend) ||
+               (TargetBackend == backend::all && !isESIMD);
       });
 }