[sanitizer] Correct name length computation for some Fuchsia vmos

[cryptoad]

Summary

This was missed during the review of D38595, but the vmo name size computation
should use internal_strlen, not sizeof, otherwise we end up with 7 character
names.

[mcgrathr]

lgtm

lib/sanitizer_common/sanitizer_fuchsia.cc

static uptr DoMmapFixedOrDie(zx_handle_t vmar, uptr fixed_addr, uptr map_size,
   map_size = RoundUpTo(map_size, PAGE_SIZE);
   zx_handle_t vmo;
   zx_status_t status = _zx_vmo_create(map_size, 0, &vmo);
   if (status != ZX_OK) {
     if (status != ZX_ERR_NO_MEMORY || die_for_nomem)
       ReportMmapFailureAndDie(map_size, name, "zx_vmo_create", status);
     return 0;
   }
-  _zx_object_set_property(vmo, ZX_PROP_NAME, name, sizeof(name) - 1);
+  _zx_object_set_property(vmo, ZX_PROP_NAME, name, internal_strlen(name));
   DCHECK_GE(base + size_, map_size + offset);
   uintptr_t addr;
 
   status = _zx_vmar_map(
       vmar, offset, vmo, 0, map_size,
       ZX_VM_FLAG_PERM_READ | ZX_VM_FLAG_PERM_WRITE | ZX_VM_FLAG_SPECIFIC,
       &addr);
   _zx_handle_close(vmo);