[dfsan] Fix build after r346262

compiler-rt/lib/dfsan/dfsan.cc:426:3: error: call to 'InitializePlatformEarly' is ambiguous
  InitializePlatformEarly();
  ^~~~~~~~~~~~~~~~~~~~~~~
compiler-rt/lib/dfsan/../sanitizer_common/sanitizer_common.h:901:6: note: candidate function
void InitializePlatformEarly();
     ^
compiler-rt/lib/dfsan/dfsan.cc:391:13: note: candidate function
static void InitializePlatformEarly() {
            ^

llvm-svn: 346264