[SYCL][E2E] Add selected targets to available features set (#16860)

This resolves two issues: 
- Currently in `build-only` XFAILs for target features don't trigger
because the target feature is not in the available features set.
- Being able to use the target feature instead of `any-target-is` for
`%if` conditions in run lines allows us to only add the bit enclosed in
the condition if that target is selected. So for example if a particular
target is available, but it is marked as xfail/unsupported for a given
test we dont add the bits enclosed in `%if target-`. On the other hand
if this were enclosed with `%if any-target-is-`, we would add it, which
is not always desirable.

Author: ayylol

sycl/test-e2e/Regression/multiple-targets.cpp

@@ -3,16 +3,16 @@
 // The test is repeated for per_kernel device code splitting.
 //
 // REQUIRES: (target-nvidia || target-amd || target-native_cpu) && any-target-is-spir
-// RUN: %clangxx -fsycl -fsycl-targets=%{sycl_triple},spir64 %if any-target-is-amd %{ %{hip_arch_opts} %} -o %t1.out %s
+// RUN: %clangxx -fsycl -fsycl-targets=%{sycl_triple},spir64 %if target-amd %{ %{hip_arch_opts} %} -o %t1.out %s
 // RUN: %{run} %t1.out
 //
-// RUN: %clangxx -fsycl -fsycl-targets=spir64,%{sycl_triple} %if any-target-is-amd %{ %{hip_arch_opts} %} -o %t2.out %s
+// RUN: %clangxx -fsycl -fsycl-targets=spir64,%{sycl_triple} %if target-amd %{ %{hip_arch_opts} %} -o %t2.out %s
 // RUN: %{run} %t2.out
 //
-// RUN: %clangxx -fsycl -fsycl-targets=%{sycl_triple},spir64 %if any-target-is-amd %{ %{hip_arch_opts} %} -fsycl-device-code-split=per_kernel -o %t3.out %s
+// RUN: %clangxx -fsycl -fsycl-targets=%{sycl_triple},spir64 %if target-amd %{ %{hip_arch_opts} %} -fsycl-device-code-split=per_kernel -o %t3.out %s
 // RUN: %{run} %t3.out
 //
-// RUN: %clangxx -fsycl -fsycl-targets=spir64,%{sycl_triple} %if any-target-is-amd %{ %{hip_arch_opts} %} -fsycl-device-code-split=per_kernel -o %t4.out %s
+// RUN: %clangxx -fsycl -fsycl-targets=spir64,%{sycl_triple} %if target-amd %{ %{hip_arch_opts} %} -fsycl-device-code-split=per_kernel -o %t4.out %s
 // RUN: %{run} %t4.out
 
 #include <sycl/detail/core.hpp>

sycl/test-e2e/format.py

@@ -221,6 +221,9 @@ def execute(self, test, litConfig):
                 build_targets.add(test.config.backend_to_target[backend])
 
         triples = set(test.config.target_to_triple[t] for t in build_targets)
+        test.config.available_features = test.config.available_features.union(
+            build_targets
+        )
 
         substitutions = lit.TestRunner.getDefaultSubstitutions(test, tmpDir, tmpBase)