NaCl: Update revision in DEPS, 58979e3 -> 9f6a876
NaCl: Update revision in DEPS, 58979e3 -> 9f6a876

This pulls in the following Native Client changes:

21001da: (dschuff@chromium.org) Build the IRT with nacl-clang for x86 in gyp and SCons
9f6a876: (dschuff@chromium.org) Move CCFLAGS modifications in nacl_irt_env to after they get clobbered

Changes: https://chromium.googlesource.com/native_client/src/native_client/+log/58979e3bf7b370d716f6d56269b7bb43af9fbc01..9f6a8764c9ae8d491045c27b64634639b815f64a

BUG=none
TEST=browser_tests and nacl_integration
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:linux_chromium_dbg_32_ng,linux_arm_compile,linux_nacl_sdk_build

Review URL: https://codereview.chromium.org/1300213009

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#344655}

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