Run bpf_existence_test in mainline-postsubmit.

The TEST_MAPPING file already contains a mainline-postsubmit
stanza, but according to go/test-mapping-mainline-user-guide
this information also needs to be in AndroidTest.xml (or in
Android.bp, for tests that are not covered by an AndroidTest.xml
and where soong autogenerates the test config).

Test: m bpf_existence_test
Change-Id: I103f5fefbfefa6fd2b59ab6c209fbf1dceada4ba

tests/common/Android.bp

@@ -121,3 +121,17 @@ java_defaults {
         "framework-res",
     ],
 }
+
+// Defaults for native tests that want to run in mainline-presubmit.
+// Not widely used (or present for Java) because many of our tests have AndroidTest.xml files and
+// use the mainline-param config-descriptor metadata in AndroidTest.xml.
+cc_defaults {
+    name: "connectivity-mainline-presubmit-cc-defaults",
+    // test_mainline_modules is an array of strings. Each element in the array is a list of modules
+    // separated by "+". The modules in this list must be in alphabetical order.
+    // See SuiteModuleLoader.java.
+    // TODO: why are the modules separated by + instead of being separate entries in the array?
+    test_mainline_modules: [
+        "CaptivePortalLoginGoogle.apk+NetworkStackGoogle.apk+com.google.android.resolv.apex+com.google.android.tethering.apex",
+    ],
+}

tests/mts/Android.bp

@@ -23,6 +23,9 @@ cc_test {
         "general-tests",
         "mts-tethering",
     ],
+    defaults: [
+        "connectivity-mainline-presubmit-cc-defaults",
+    ],
     require_root: true,
     static_libs: [
         "libbase",