RESTRICT AUTOMERGE: Add symlink for mediacodec-x86_64.policy

When building for x86 *without* TARGET_2ND_ARCH set, the build fails
because the mediacodec-$(TARGET_ARCH).policy expands to
mediacodec-x86_64.policy, which doesn't exist. Create it.

Bug: 158658685
Change-Id: I11108a62fac6fc9dcf47c0acd908663e155252cd
diff --git a/services/mediacodec/seccomp_policy/mediacodec-x86_64.policy b/services/mediacodec/seccomp_policy/mediacodec-x86_64.policy
new file mode 120000
index 0000000..ab2592a
--- /dev/null
+++ b/services/mediacodec/seccomp_policy/mediacodec-x86_64.policy
@@ -0,0 +1 @@
+mediacodec-x86.policy
\ No newline at end of file