[SYCLomatic] Fix 2 coverity issues. (#2847)

Signed-off-by: Chen, Sheng S <sheng.s.chen@intel.com>

Author: ShengchenJ

clang/lib/Driver/ToolChains/Gnu.cpp

@@ -3493,7 +3493,7 @@ bool Generic_GCC::addGCCLibStdCxxIncludePaths(
 #ifdef SYCLomatic_CUSTOMIZATION
   // Detect Debian g++-multiarch-incdir.diff through the list of candidate, the
   // potential GCC version sorts in descending orde.
-  for (auto Candidate : GCCInstallation.GetCandidateVersion()) {
+  for (auto &Candidate : GCCInstallation.GetCandidateVersion()) {
     if (addLibStdCXXIncludePaths(
             LibDir.str() + "/../include/c++/" + Candidate.Text, DebianMultiarch,
             Multilib.includeSuffix(), DriverArgs, CC1Args, /*Debian=*/true))

clang/lib/Serialization/ASTReaderStmt.cpp

@@ -3177,6 +3177,7 @@ Stmt *ASTReader::ReadStmtFromStream(ModuleFile &F) {
 
     case EXPR_SYCL_UNIQUE_STABLE_ID:
       S = SYCLUniqueStableIdExpr::CreateEmpty(Context);
+      break;
 
     case EXPR_OPENACC_ASTERISK_SIZE:
       S = OpenACCAsteriskSizeExpr::CreateEmpty(Context);