Temporary workaround to trigger a rebuild of libicudata_nacl on icu version update

Temporary workaround to trigger a rebuild of libicudata_nacl on icu version update

When ICU was rolled from icu4.6 to icu52, libicudata_nacl was not rebuilt
on some build bots leading to an undefined symbol linker error (icudt52_dat
not found).

By making icudata_nacl target explicitly depend on uvernum.h, we can force
icudata_nacl target to be rebuilt when there's an ICU version change.
(a work-around suggested by Sergey).

A more fundamental fix is to change the way nacl targets determine
its dependencies See https://codereview.chromium.org/336993003/

BUG=132145
TEST=After rolling icu to 52, incremental build will not complain about missing symbol (icudt52_dat).
R=sergeyu@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=277885

[jungshik at Google, 2014-06-16 08:13:42]

Hi Sergey, 

Thank you for suggesting this work around. Can you take a look?

[jungshik at Google, 2014-06-17 17:29:37]

Ping, Sergey :-) Thanks

[Sergey Ulanov, 2014-06-17 18:15:10]

lgtm

[jungshik at Google, 2014-06-17 22:29:00]

Committed patchset #2 manually as r277885 (presubmit successful).