NaCl: Synchronise build.scons file with Gyp file

NaCl: Synchronise build.scons file with Gyp file

I moved sel_ldr_launcher_chrome.cc into the Chromium repo in r134552
but I forgot to update build.scons.  This update is necessary for
removing sel_ldr_launcher_chrome.cc from the NaCl repo because it
ensures that the 'launch_nacl_process' variable (which module_ppapi.cc
assigns to) will be defined.  (The alternative would be to
conditionalise the assignment of 'launch_nacl_process' in
module_ppapi.cc.)

BUG=http://code.google.com/p/nativeclient/issues/detail?id=2750
TEST=NaCl's Scons build


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=134619

[bbudge, 2012-04-30 20:59:50]

lgtm

[commit-bot: I haz the power, 2012-04-30 21:00:26]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mseaborn@chromium.org/10261016/1

[commit-bot: I haz the power, 2012-04-30 22:36:41]

Change committed as 134619