This corrects a "cleanup" mistake in line 414/417 of https://codereview.chromium.org/1838753002/diff/120001/src/IceTargetLoweringX8664.cpp .

This wasn't caught before because "make presubmit" doesn't run any sandboxed x86-64 tests.  So we add that to the presubmit script.

In addition, the "make check-spec" is changed to run each spec component via the "--run" flag of szbuild_spec2k.py.  Otherwise, the makefile was hard-coding running the native binary setup instead of the sandboxed or nonsfi setup.

BUG= none
R=jpp@chromium.org

Review URL: https://codereview.chromium.org/1852713004 .