Split up xfa/fgas/BUILD.gn by crt/ and font/ directories

Currently, two are at top-level xfa/fgas, and two are below it in
subdirectories. Be consistent.

Change-Id: I8cf4a177f04d3db06de67e850eb032e9561b26eb
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/75070
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index c2d415d..b69dda6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -271,7 +271,7 @@
         "core/fxcrt/css:unittests",
         "fxbarcode:unittests",
         "xfa/fde:unittests",
-        "xfa/fgas:unittests",
+        "xfa/fgas/crt:unittests",
         "xfa/fgas/layout:unittests",
         "xfa/fxfa:unittests",
         "xfa/fxfa/fm2js:unittests",