[SYCL][NFC] Wrap classes in .cpp into a namespace to disable external linkage. (#1776)

Signed-off-by: Konstantin S Bobrovsky <konstantin.s.bobrovsky@intel.com>

Author: kbobrovs

clang/lib/CodeGen/CGSYCLRuntime.cpp

@@ -20,6 +20,8 @@
 using namespace clang;
 using namespace CodeGen;
 
+namespace {
+
 /// Various utilities.
 /// TODO partially duplicates functionality from SemaSYCL.cpp, can be shared.
 class Util {
@@ -52,6 +54,8 @@ const char *WG_SCOPE_MD_ID = "work_group_scope";
 const char *WI_SCOPE_MD_ID = "work_item_scope";
 const char *PFWI_MD_ID = "parallel_for_work_item";
 
+} // anonymous namespace
+
 bool CGSYCLRuntime::actOnFunctionStart(const FunctionDecl &FD,
                                        llvm::Function &F) {
   SYCLScopeAttr *Scope = FD.getAttr<SYCLScopeAttr>();

clang/lib/Sema/SemaSYCL.cpp

@@ -54,6 +54,8 @@ enum KernelInvocationKind {
 const static std::string InitMethodName = "__init";
 const static std::string FinalizeMethodName = "__finalize";
 
+namespace {
+
 /// Various utilities.
 class Util {
 public:
@@ -91,6 +93,8 @@ class Util {
                                      ArrayRef<Util::DeclContextDesc> Scopes);
 };
 
+} // anonymous namespace
+
 // This information is from Section 4.13 of the SYCL spec
 // https://www.khronos.org/registry/SYCL/specs/sycl-1.2.1.pdf
 // This function returns false if the math lib function