[cleanup] Move comment closer to code it describes

Bug: v8:8562
Change-Id: I7f65b4cd92bb08434afe3a18512223adaf47feec
Reviewed-on: https://chromium-review.googlesource.com/c/1470112
Commit-Queue: Maciej Goszczycki <goszczycki@google.com>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59577}

BUILD.gn

@@ -171,13 +171,11 @@ declare_args() {
   # setting the "check_v8_header_includes" gclient variable to run a
   # specific hook).
   v8_check_header_includes = false
-
-  # We reuse the snapshot toolchain for building torque and other generators to
-  # avoid building v8_libbase on the host more than once. On mips with big
-  # endian, the snapshot toolchain is the target toolchain and, hence, can't be
-  # used.
 }
 
+# We reuse the snapshot toolchain for building torque and other generators to
+# avoid building v8_libbase on the host more than once. On mips with big endian,
+# the snapshot toolchain is the target toolchain and, hence, can't be used.
 v8_generator_toolchain = v8_snapshot_toolchain
 if (host_cpu == "x64" &&
     (v8_current_cpu == "mips" || v8_current_cpu == "mips64")) {