Changes have been made in Git (master):

commit effd35c63173dc95ad21edc15a547359e11eb803
Author: Michael J Rubinsky <mrubinsk@horde.org>
Date:   Sat Dec 3 12:58:46 2016 -0500

     Bug: 14532 Fix this test for 32bit systems also.

     I don't have the client I used to generate the base64 string for this
     test any longer, so use a slight hack to make sure the value is taken
     as a 32bit unsigned int even though PHP stores it internally as signed.

  framework/ActiveSync/test/Horde/ActiveSync/UtilsTest.php | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

http://github.com/horde/horde/commit/effd35c63173dc95ad21edc15a547359e11eb803

Changes have been made in Git (master):

commit fa72f5da06d1657d69cc69184f117c8d7c6d4e67
Author: Michael J Rubinsky <mrubinsk@horde.org>
Date:   Sat Dec 3 12:08:37 2016 -0500

     Bug: 14532 Use new fixture that's safe for 32 bit arch.

     Note that don't need to change the actual code generating/using
     these values since the value in question is also generated on the
     same server.

  framework/ActiveSync/test/Horde/ActiveSync/UtilsTest.php | 16 
+++++++++-------
  1 file changed, 9 insertions(+), 7 deletions(-)

http://github.com/horde/horde/commit/fa72f5da06d1657d69cc69184f117c8d7c6d4e67

i get:
There was 1 failure:
1) Horde_ActiveSync_UtilsTest::testBase64Uri
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
  Array (
      'ProtVer' => '12.1'
      'Cmd' => 'Provision'
      'Locale' => 1033
      'DeviceId' => 'ae4ecd19f592ba5657706ff74cf09bac'
-    'PolicyKey' => 3897326716.0
+    'PolicyKey' => -397640580
      'DeviceType' => 'PPC'
  )

during a build on a 32bit system.
maybe you could create a check for 64bit