[NaCl SDK] Consistently honor LDFLAGS in SDK build system

[NaCl SDK] Consistently honor LDFLAGS in SDK build system

host_gcc.mk was already honoring this variable, as was
the SO_RULE in nacl_gcc.mk but the LINK_RULE for nacl_gcc.mk
and nacl_llvm.mk was ignoring LDFLAGS.

Committed: https://crrev.com/aad9f37acd056092bf0ee579c328ed024ef41609
Cr-Commit-Position: refs/heads/master@{#318586}

[Sam Clegg, 2015-02-27 00:30:51]

sbc@chromium.org changed reviewers:
+ binji@chromium.org

[binji, 2015-02-27 00:34:22]

lgtm

[Sam Clegg, 2015-02-28 01:09:04]

The CQ bit was checked by sbc@chromium.org

[Sam Clegg, 2015-02-28 01:09:05]

The CQ bit was unchecked by sbc@chromium.org

[Sam Clegg, 2015-02-28 01:24:36]

The CQ bit was checked by sbc@chromium.org

[commit-bot: I haz the power, 2015-02-28 01:25:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/960963003/1

[commit-bot: I haz the power, 2015-02-28 03:09:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-28 03:10:06]

Patchset 1 (id:??) landed as
https://crrev.com/aad9f37acd056092bf0ee579c328ed024ef41609
Cr-Commit-Position: refs/heads/master@{#318586}