drop BASE_VER define

The libchrome pc files export BASE_VER define themselves now, so no
need for us to do it.

BUG=chromium:331128
TEST=`cbuildbot chromiumos-sdk` still works

Change-Id: I3301ad41f3dc6399a8fa65a5edf66080454a91e7
Reviewed-on: https://chromium-review.googlesource.com/185062
Reviewed-by: Daniel Erat <derat@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/libchromeos.gypi b/libchromeos.gypi
index 5bfd9b2..a15b1fb 100644
--- a/libchromeos.gypi
+++ b/libchromeos.gypi
@@ -8,9 +8,6 @@
       # Need to sort that out before we enable this.
       'enable_werror': 0,
     },
-    'defines': [
-      'BASE_VER=<(libbase_ver)',
-    ],
     'include_dirs': [
       '../libchromeos',
     ],