Revert "Revert "Upgrade to 5.0.71.48"" DO NOT MERGE

This reverts commit f2e3994fa5148cc3d9946666f0b0596290192b0e,
and updates the x64 makefile properly so it doesn't break that
build.

FPIIM-449

Change-Id: Ib83e35bfbae6af627451c926a9650ec57c045605
(cherry picked from commit 109988c7ccb6f3fd1a58574fa3dfb88beaef6632)
diff --git a/build/isolate.gypi b/build/isolate.gypi
index 5d30005..546870a 100644
--- a/build/isolate.gypi
+++ b/build/isolate.gypi
@@ -71,12 +71,15 @@
         '--config-variable', 'OS=<(OS)',
         '--config-variable', 'asan=<(asan)',
         '--config-variable', 'cfi_vptr=<(cfi_vptr)',
+        '--config-variable', 'gcmole=<(gcmole)',
+        '--config-variable', 'has_valgrind=<(has_valgrind)',
         '--config-variable', 'icu_use_data_file_flag=0',
         '--config-variable', 'msan=<(msan)',
         '--config-variable', 'tsan=<(tsan)',
         '--config-variable', 'component=<(component)',
         '--config-variable', 'target_arch=<(target_arch)',
         '--config-variable', 'use_custom_libcxx=<(use_custom_libcxx)',
+        '--config-variable', 'v8_separate_ignition_snapshot=<(v8_separate_ignition_snapshot)',
         '--config-variable', 'v8_use_external_startup_data=<(v8_use_external_startup_data)',
         '--config-variable', 'v8_use_snapshot=<(v8_use_snapshot)',
       ],