[ELF] - An attemp to fix builld bit after r368260

BB: http://lab.llvm.org:8011/builders/lld-perf-testsuite/builds/17577/steps/build-bin%2Flld/logs/stdio

The error is:
/home/buildslave/slave_as-bldslv8/lld-perf-testsuite/llvm/include/llvm/Object/ELF.h:67:14:
error: 'static' function 'defaultWarningHandler' declared in header file should be declared 'static inline' [-Werror,-Wunneeded-internal-declaration]
static Error defaultWarningHandler(const Twine &Msg) { return createError(Msg); }
             ^

llvm-svn: 368262