tests: Pick up testdata with LOCAL_TEST_DATA.

Also push the testdata in AndroidTest.xml for `atest`.

LOCAL_TEST_DATA was added in commit [1], which ships testdata next to
native tests.

With this CL,
 1) manually sync-ing via `adb sync` and running tests with `adb shell`
    keep working.
 2) both of 32- and 64-bit recovery_{unit,component}_test now work in
    APCT continuous tests. Note that 64-bit tests were failing
    previously in APCT, due to missing testdata.
 3) `atest recovery_unit_test` works, as the testdata gets pushed to
    /data/local/tmp.

[1] commit d07ba4e2a625a8f000d042c1953adb612bccbbe2 in
https://android-review.googlesource.com/c/platform/build/+/312567.

Bug: 77320514
Test: Build recovery_{unit,component,manual}_test. Setup the test via
      `adb sync data`. Run both of 32- and 64-bit versions on device.
Test: Build and run recovery_host_test on host, for both of 32- and
      64-bit versions.
Test: `atest recovery_component_test`
Change-Id: Ie54037726043a3a659a80030b83db1f8c1de318d
diff --git a/tests/common/test_constants.h b/tests/common/test_constants.h
index 514818e..b6c27a7 100644
--- a/tests/common/test_constants.h
+++ b/tests/common/test_constants.h
@@ -17,10 +17,10 @@
 #ifndef _OTA_TEST_CONSTANTS_H
 #define _OTA_TEST_CONSTANTS_H
 
-#include <stdlib.h>
-
 #include <string>
 
+#include <android-base/file.h>
+
 // Zip entries in ziptest_valid.zip.
 static const std::string kATxtContents("abcdefghabcdefgh\n");
 static const std::string kBTxtContents("abcdefgh\n");
@@ -32,14 +32,9 @@
 // echo -n -e "abcdefgh\n" | sha1sum
 static const std::string kBTxtSha1Sum("e414af7161c9554089f4106d6f1797ef14a73666");
 
-static std::string from_testdata_base(const std::string& fname) {
-#ifdef __ANDROID__
-  static std::string data_root = getenv("ANDROID_DATA");
-#else
-  static std::string data_root = std::string(getenv("ANDROID_PRODUCT_OUT")) + "/data";
-#endif
-
-  return data_root + "/nativetest/recovery/testdata/" + fname;
+[[maybe_unused]] static std::string from_testdata_base(const std::string& fname) {
+  static std::string exec_dir = android::base::GetExecutableDirectory();
+  return exec_dir + "/testdata/" + fname;
 }
 
 #endif  // _OTA_TEST_CONSTANTS_H