Make helpers static. clang-tools edition.

Also purge dead code found by it. NFC.

llvm-svn: 232948
diff --git a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
index 398d2d0..a9437a8 100644
--- a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
+++ b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
@@ -215,7 +215,7 @@
   OS.flush();
 }
 
-std::unique_ptr<ClangTidyOptionsProvider> createOptionsProvider() {
+static std::unique_ptr<ClangTidyOptionsProvider> createOptionsProvider() {
   ClangTidyGlobalOptions GlobalOptions;
   if (std::error_code Err = parseLineFilter(LineFilter, GlobalOptions)) {
     llvm::errs() << "Invalid LineFilter: " << Err.message() << "\n\nUsage:\n";
@@ -261,7 +261,7 @@
                                                 OverrideOptions);
 }
 
-int clangTidyMain(int argc, const char **argv) {
+static int clangTidyMain(int argc, const char **argv) {
   CommonOptionsParser OptionsParser(argc, argv, ClangTidyCategory);
 
   auto OptionsProvider = createOptionsProvider();