[gn build] Reformat all files

Ran `git ls-files '*.gn' '*.gni' | xargs llvm/utils/gn/gn.py format`.

Author: nico

llvm/utils/gn/secondary/llvm/tools/llvm-diff/lib/BUILD.gn

@@ -7,9 +7,9 @@ static_library("lib") {
   sources = [
     "DiffConsumer.cpp",
     "DiffConsumer.h",
-    "DifferenceEngine.cpp",
-    "DifferenceEngine.h",
     "DiffLog.cpp",
     "DiffLog.h",
+    "DifferenceEngine.cpp",
+    "DifferenceEngine.h",
   ]
 }