add seccomp-tests

BUG: 27457324

default.xml

@@ -270,6 +270,7 @@
   <project path="external/rootdev" name="platform/external/rootdev" />
   <project path="external/safe-iop" name="platform/external/safe-iop" groups="pdk" />
   <project path="external/scrypt" name="platform/external/scrypt" groups="pdk" />
+  <project path="external/seccomp-tests" name="platform/external/seccomp-tests" />
   <project path="external/selinux" name="platform/external/selinux" groups="pdk" />
   <project path="external/shflags" name="platform/external/shflags" groups="pdk" />
   <project path="external/sfntly" name="platform/external/sfntly" groups="pdk,qcom_msm8x26" />