format GN files, and invert if->config to config->if

Both if (...) { config ... } else { config ... } and config { if (...) { ...}
else { ... } } work.  We just happen to do the if inside the config more often
than the other way around.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2347953002

Review-Url: https://codereview.chromium.org/2347953002
diff --git a/BUILD.gn b/BUILD.gn
index 23fca35..9a9157e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -481,7 +481,8 @@
       "src/ports/SkTypeface_win_dw.cpp",
       "src/xps/SkDocument_XPS.cpp",
     ]
-    sources -= [ get_path_info("src/utils/SkThreadUtils_pthread.cpp", "abspath") ]
+    sources -=
+        [ get_path_info("src/utils/SkThreadUtils_pthread.cpp", "abspath") ]
   } else {
     sources += [
       "src/ports/SkOSFile_posix.cpp",