Make crash diagnostics on Windows the tiniest bit more useful

This escapes any backslashes in the executable path and fixes an issue
with a trailing quote when the main file name had to be quoted during
printing.

It's impossible to test this without putting backslashes or quotes into
the executable path, so I didn't add automated tests.

The crash diagnostics are still only useful if you're using bash on
Windows, though.  This should probably be writing a batch file instead.

llvm-svn: 214924

clang/lib/Driver/Driver.cpp

@@ -548,6 +548,8 @@ void Driver::generateCompilationDiagnostics(Compilation &C,
         StringRef NewFilename = llvm::sys::path::filename(*it);
         I = StringRef(Cmd).rfind(OldFilename);
         E = I + OldFilename.size();
+        if (E + 1 < Cmd.size() && Cmd[E] == '"')
+          ++E;  // Replace a trailing quote if present.
         I = Cmd.rfind(" ", I) + 1;
         Cmd.replace(I, E - I, NewFilename.data(), NewFilename.size());
         if (!VFS.empty()) {

clang/lib/Driver/Job.cpp

@@ -95,7 +95,8 @@ static void PrintArg(raw_ostream &OS, const char *Arg, bool Quote) {
 
 void Command::Print(raw_ostream &OS, const char *Terminator, bool Quote,
                     bool CrashReport) const {
-  OS << " \"" << Executable << '"';
+  // Always quote the exe.
+  PrintArg(OS, Executable, /*Quote=*/true);
 
   for (size_t i = 0, e = Arguments.size(); i < e; ++i) {
     const char *const Arg = Arguments[i];