[Support] Factorize more cases of style checks to use is_style_windows. NFC.

[mstorsjo]

Summary

These conditions apply in the same way for Windows path styles with
forward slashes.

After D112289, the only remaining uses of real_path are in
preferred_separator, get_separator (and in remove_dots which doesn't
compare literal enum values though).

[dexonsmith]

FYI, I'm going to fold these into https://reviews.llvm.org/D112289 when I push in a moment.

[dexonsmith]

In D112786#3097347, @dexonsmith wrote:

FYI, I'm going to fold these into https://reviews.llvm.org/D112289 when I push in a moment.

I pushed that in 99023627010bbfefb71e25a2b4d056de1cbd354e.

[mstorsjo]

Landed as part of D112289.

llvm/lib/Support/Path.cpp

namespace {
 
   inline Style real_style(Style style) {
     if (is_style_posix(style))
       return Style::posix;
     return Style::windows;
   }
 
   inline const char *separators(Style style) {
-    if (real_style(style) == Style::windows)
+    if (is_style_windows(style))
       return "\\/";
     return "/";
   }
 
   inline char preferred_separator(Style style) {
     if (real_style(style) == Style::windows)
       return '\\';
     return '/';
void native(const Twine &path, SmallVectorImpl<char> &result, Style style) {
   result.clear();
   path.toVector(result);
   native(result, style);
 }
 
 void native(SmallVectorImpl<char> &Path, Style style) {
   if (Path.empty())
     return;
-  if (real_style(style) == Style::windows) {
+  if (is_style_windows(style)) {
     std::replace(Path.begin(), Path.end(), '/', '\\');
     if (Path[0] == '~' && (Path.size() == 1 || is_separator(Path[1], style))) {
       SmallString<128> PathHome;
       home_directory(PathHome);
       PathHome.append(Path.begin() + 1, Path.end());
       Path = PathHome;
     }
   } else {
     std::replace(Path.begin(), Path.end(), '\\', '/');
   }
 }
 
 std::string convert_to_slash(StringRef path, Style style) {
-  if (real_style(style) != Style::windows)
+  if (!is_style_windows(style))
     return std::string(path);
 
   std::string s = path.str();
   std::replace(s.begin(), s.end(), '\\', '/');
   return s;
 }
 
 StringRef filename(StringRef path, Style style) { return *rbegin(path, style); }