Fix typos in BUILD.gn source lists

"foo,cc" is not the same as "foo.cc"

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/326193002

Patch from James Robinson <jamesr@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21765 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Set SAHF flag correctly for ia32

sahf flag will not be set for ia32 on some old platform because some old processors does not support CPUID's extended features.
This also avoids redundant cpuid check in ia32 for sahf.

BUG=
R=danno@chromium.org

Review URL: https://codereview.chromium.org/298823008

Patch from Weiliang Lin <weiliang.lin@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21766 ce2b1a6d-e550-0410-aec6-3dcde31c8c00