Remove obsolete -malign-natural on Mac OS X from SDK, too

...causes "clang: error: unknown argument: '-malign-natural'
[-Wunused-command-line-argument-hard-error-in-future]; clang: note: this will be
a hard error (cannot be downgraded to a warning) in the future" at least with
"Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)", and last
mention of -malign-natural in solenv/gbuild was removed with
4ea84822b1b638a61495af5006041bea8db8a3eb "OSX: drop -malign-natural flag for
non-clang compilers."

Change-Id: I0db1de484e45ba3eddf113392da71f20d099e9b5