Don't use std::errc.

As noted on Errc.h:

// * std::errc is just marked with is_error_condition_enum. This means that
//   common patters like AnErrorCode == errc::no_such_file_or_directory take
//   4 virtual calls instead of two comparisons.

And on some libstdc++ those virtual functions conclude that

------------------------
int main() {
  std::error_code foo = std::make_error_code(std::errc::no_such_file_or_directory);
  return foo == std::errc::no_such_file_or_directory;
}
-------------------------

should exit with 0.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@239684 91177308-0d34-0410-b5e6-96231b3b80d8

lib/StaticAnalyzer/Core/HTMLDiagnostics.cpp

@@ -22,6 +22,7 @@
 #include "clang/Rewrite/Core/Rewriter.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "llvm/Support/Errc.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
@@ -306,7 +307,7 @@ void HTMLDiagnostics::ReportDiag(const PathDiagnostic& D,
                                                FD,
                                                llvm::sys::fs::F_RW |
                                                llvm::sys::fs::F_Excl);
-          if (EC && EC != std::errc::file_exists) {
+          if (EC && EC != llvm::errc::file_exists) {
               llvm::errs() << "warning: could not create file '" << Model
                            << "': " << EC.message() << '\n';
               return;