Fix output path of run_sksllex to match what the script does

This doesn't get rid of the warning about multiple rules, but it does
ensure the build reaches steady state (after two runs).

Change-Id: I9a90b8e310225fb5cab544a86dd271162d0fe0df
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/372122
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index dd12bd9..cf4f350 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -562,8 +562,7 @@
     # GN insists its outputs should go somewhere underneath target_out_dir, so we trick it with a
     # path that starts with target_out_dir and then uses ".." to back up into the src dir.
     outputs = [
-      "$target_out_dir/" +
-          rebase_path("src/sksl/lex/SkSLLexer.h", target_out_dir),
+      "$target_out_dir/" + rebase_path("src/sksl/SkSLLexer.h", target_out_dir),
       # the script also modifies the corresponding .cpp file, but if we tell GN that it gets
       # confused due to the same file being named by two different paths
     ]