[Driver][SYCL] Additional dependency gen step is part of offload toolchain (#4456)

The additional preprocessing step which is created that creates the
dependency information for the host compilation needs to be properly
setup as part of the SYCL offloading toolchain.  Without doing so, not
all of the dependencies (headers for instance) are properly pulled in.

Author: mdtoguchi

clang/lib/Driver/Driver.cpp

@@ -5510,8 +5510,11 @@ void Driver::BuildActions(Compilation &C, DerivedArgList &Args,
       if (Phase == phases::Preprocess && Args.hasArg(options::OPT_fsycl) &&
           Args.hasArg(options::OPT_M_Group) &&
           !Args.hasArg(options::OPT_fno_sycl_use_footer)) {
-        Actions.push_back(
-            C.MakeAction<PreprocessJobAction>(Current, types::TY_Dependencies));
+        Action *PreprocessAction =
+            C.MakeAction<PreprocessJobAction>(Current, types::TY_Dependencies);
+        PreprocessAction->propagateHostOffloadInfo(Action::OFK_SYCL,
+                                                   /*BoundArch=*/nullptr);
+        Actions.push_back(PreprocessAction);
       }
 
       // FIXME: Should we include any prior module file outputs as inputs of

clang/test/Driver/sycl-int-footer.cpp

@@ -71,9 +71,11 @@
 /// Check behaviors for dependency generation
 // RUN:  %clangxx -fsycl -MD -c %s -### 2>&1 \
 // RUN:   | FileCheck -check-prefix DEP_GEN %s
-// DEP_GEN:  clang{{.*}} "-Eonly"
+// DEP_GEN:  clang{{.*}} "-fsycl-is-host"
+// DEP_GEN-SAME: "-Eonly"
 // DEP_GEN-SAME: "-dependency-file"
 // DEP_GEN-SAME: "-MT"
+// DEP_GEN-SAME: "-internal-isystem" "{{.*}}{{[/\\]+}}include{{[/\\]+}}sycl"
 // DEP_GEN-SAME: "-x" "c++" "[[INPUTFILE:.+\.cpp]]"
 // DEP_GEN: append-file{{.*}} "[[INPUTFILE]]"
 // DEP_GEN-NOT: clang{{.*}} "-dependency-file"