Everywhere: Turn #if *_DEBUG into dbgln_if/if constexpr

Author: https://github.com/gunnarbeutner
Commit: 6cf59b6ae9
Pull-request: https://github.com/SerenityOS/serenity/pull/6796

Userland/DevTools/HackStudio/Git/DiffViewer.cpp

@@ -140,10 +140,10 @@ void DiffViewer::set_content(const String& original, const String& diff)
     m_original_lines = split_to_lines(original);
     m_hunks = Diff::parse_hunks(diff);
 
-#if DIFF_DEBUG
-    for (size_t i = 0; i < m_original_lines.size(); ++i)
-        dbgln("{}:{}", i, m_original_lines[i]);
-#endif
+    if constexpr (DIFF_DEBUG) {
+        for (size_t i = 0; i < m_original_lines.size(); ++i)
+            dbgln("{}:{}", i, m_original_lines[i]);
+    }
 }
 
 DiffViewer::DiffViewer()