Use VDSO for clock_gettime(2) and gettimeofday(2).

Bug: 15387103

(cherry picked from commit 625993dfbb085a3cde7492eda8ec1cdc1ee39a78)

Change-Id: I0e156d7049ba1495902259071a96936592e74025
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 11585af..0b99d20 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -156,10 +156,7 @@
 }
 
 bool ElfReader::VerifyElfHeader() {
-  if (header_.e_ident[EI_MAG0] != ELFMAG0 ||
-      header_.e_ident[EI_MAG1] != ELFMAG1 ||
-      header_.e_ident[EI_MAG2] != ELFMAG2 ||
-      header_.e_ident[EI_MAG3] != ELFMAG3) {
+  if (memcmp(header_.e_ident, ELFMAG, SELFMAG) != 0) {
     DL_ERR("\"%s\" has bad ELF magic", name_);
     return false;
   }