Label the dynamic linker in the runtime APEX correctly

e2bc9fe9d5ac82457bc6050bf705ff43a1b05cbf in platform/art project added
the dynamic linker to the runtime APEX. Since the dynamic linker has
been labeled as 'system_linker_exec' so does the linker in the APEX.

Bug: 120266448
Test: ls -Z /apex/com.android.runtime/bin/linker
u:object_r:system_linker_exec:s0 /apex/com.android.runtime/bin/linker

Change-Id: I243b86a74d94058b3283830c32232c6584639ff3

apex/com.android.runtime.debug-file_contexts

@@ -5,5 +5,6 @@
 /bin/dex2oat(d)?         u:object_r:dex2oat_exec:s0
 /bin/dexoptanalyzer(d)?  u:object_r:dexoptanalyzer_exec:s0
 /bin/profman(d)?         u:object_r:profman_exec:s0
+/bin/linker(64)?         u:object_r:system_linker_exec:s0
 /lib(64)?(/.*)?          u:object_r:system_lib_file:s0
 /etc/tz(/.*)?            u:object_r:system_zoneinfo_file:s0

apex/com.android.runtime.release-file_contexts

@@ -5,5 +5,6 @@
 /bin/dex2oat             u:object_r:dex2oat_exec:s0
 /bin/dexoptanalyzer      u:object_r:dexoptanalyzer_exec:s0
 /bin/profman             u:object_r:profman_exec:s0
+/bin/linker(64)?         u:object_r:system_linker_exec:s0
 /lib(64)?(/.*)?          u:object_r:system_lib_file:s0
 /etc/tz(/.*)?            u:object_r:system_zoneinfo_file:s0