Cherry-pick upstream r237073

Cherry-pick upstream r237073

Allow empty assembly string literal with -fno-gnu-inline-asm

Empty assembly string will not introduce assembly code in the output
binary and it is often used as a trick in the header to disable
optimizations. It doesn't conflict with the purpose of the option so it
is allowed with -fno-gnu-inline-asm flag.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237073 91177308-0d34-0410-b5e6-96231b3b80d8

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4333
R=dschuff@chromium.org

Committed: 25662b2f69a0a33aeea5f88008df8d48525064ad

[Petr Hosek, 2015-11-07 23:01:08]

Description was changed from

==========
Cherry-pick upstream r237073

Allow empty assembly string literal with -fno-gnu-inline-asm

Empty assembly string will not introduce assembly code in the output
binary and it is often used as a trick in the header to disable
optimizations. It doesn't conflict with the purpose of the option so it
is allowed with -fno-gnu-inline-asm flag.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237073
91177308-0d34-0410-b5e6-96231b3b80d8

BUG=none
R=dschuff@chromium.org
==========

to

==========
Cherry-pick upstream r237073

Allow empty assembly string literal with -fno-gnu-inline-asm

Empty assembly string will not introduce assembly code in the output
binary and it is often used as a trick in the header to disable
optimizations. It doesn't conflict with the purpose of the option so it
is allowed with -fno-gnu-inline-asm flag.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237073
91177308-0d34-0410-b5e6-96231b3b80d8

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4333
R= dschuff@chromium.org
==========

[Derek Schuff, 2015-11-11 22:42:38]

lgtm

[Petr Hosek, 2015-11-12 01:16:25]

Committed patchset #1 (id:1) manually as
25662b2f69a0a33aeea5f88008df8d48525064ad (presubmit successful).