PNaCl: Update llvm revision in pnacl/COMPONENT_REVISIONS
PNaCl: Update llvm revision in pnacl/COMPONENT_REVISIONS

This pulls in the following LLVM changes:

2dc38a2: (smklein@chromium.org) Remove std::move on return when unnecessary.
a6f5a69: (smklein@chromium.org) PNaCl dynamic linking: Allow relocations of const variables.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4351
TEST= PNaCl toolchain trybots
TBR=mseaborn@chromium.org

Review URL: https://codereview.chromium.org/1749993004 .

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client