Fix untrusted.gypi and build_nexe.py

Fix untrusted.gypi and build_nexe.py

A prior version of this change was commited as r13485 and reverted as
r13506.  In the meantime, functionality was added to fix a bug where
source files with the same name would overwrite eachother's object
files.

BUG=none
R=bradnelson@google.com, dschuff@chromium.org

Committed: https://src.chromium.org/viewvc/native_client?view=rev&revision=13512

[bradn, 2014-07-18 22:54:32]

lgtm

[Derek Schuff, 2014-07-18 23:07:28]

lgtm

[Nick Bray (chromium), 2014-07-21 17:32:59]

Committed patchset #1 manually as r13512 (presubmit successful).

[Mark Seaborn, 2014-07-25 16:45:17]

When rolling DEPS, I see this compile failure:

FAILED: E:\b\depot_tools\python276_bin\python.exe gyp-win-tool action-wrapper
environment.x86
icuuc_nacl_target_build_newlib_plib_ce70c0dab4349afb56b95a15e808ff16..rsp
..\..\third_party\icu
source/common/putil.cpp:638:12: error: 'timezone' does not refer to a value
    return U_TIMEZONE;
           ^
source/common/putilimp.h:135:23: note: expanded from macro 'U_TIMEZONE'
#   define U_TIMEZONE timezone
                      ^
E:/b/build/slave/win/build/src/out/Release/gen/sdk/win_x86/pnacl_newlib/usr/include\sys/time.h:41:8:
note: declared here
struct timezone {
       ^
1 error generated.
...
FAILED: Command
'..\..\out\Release\gen\sdk\win_x86\pnacl_newlib\bin\pnacl-clang++ -c
source/common/putil.cpp -o
../../out/Release/obj/third_party/icu/icuuc_nacl.gen/pnacl_newlib-pnacl/icuuc_nacl/putil_a4b8bb19.o
...

(from
http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_rel/buil...
and https://codereview.chromium.org/422433003/)

Since this is in 'icu', and you had problems with 'icu', is this NaCl change the
cause?

Maybe you've made 'icu' changes in Chromium that LKGR hasn't caught up with?