Avoid some aliasing in buildbot "BUILD_STEP" printouts for pnacl bots.
Avoid some aliasing in buildbot "BUILD_STEP" printouts for pnacl bots.

Previously, --nacl_glibc was not considered in naming the BUILD_STEP,
so the buildbot log parser would be confused and show the non---nacl_glibc
logs in the --nacl_glibc step.

BUG= none (but confusing logs)
TEST= pnacl/test.sh test-x86-64-browser-glibc.

Review URL: https://chromiumcodereview.appspot.com/9692004

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@7999 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client