Fix path in BUILD.gn file.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 3fb53749751442fae268f6f15b720f065f4d0540..e4e0b60628d9aa45f5436424b480dd5d3f8baf9b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -646,9 +646,9 @@ static_library("fxcrt") {
   ]
   if (pdf_enable_xfa) {
     sources += [
+      "core/fxcrt/fx_arabic.cpp",
       "core/fxcrt/fx_arabic.h",
       "core/fxcrt/fx_basic_maps.cpp",
-      "core/fxcrt/include/fx_arabic.cpp",
       "core/fxcrt/include/fx_arb.h",
     ]
   }