Update check_target_files_vintf to check the last line of stdout.

More output is now produced on stdout by checkvintf.
Update logic to compare against the last line for incompatible.

Fixes the following tests:
test_check_target_files_vintf.CheckTargetFilesVintfTest#test_CheckVintf_kernel_incompat
test_check_target_files_vintf.CheckTargetFilesVintfTest#test_CheckVintf_matrix_incompat
test_check_target_files_vintf.CheckTargetFilesVintfTest#test_CheckVintf_sku_incompat

Bug: 251221029
Test: atest releasetools_test
Change-Id: I592acf9a3868e2a60e203b2201e7fadcbb0e7f04
diff --git a/tools/releasetools/check_target_files_vintf.py b/tools/releasetools/check_target_files_vintf.py
index 4a2a905..63a6cf7 100755
--- a/tools/releasetools/check_target_files_vintf.py
+++ b/tools/releasetools/check_target_files_vintf.py
@@ -142,9 +142,10 @@
     command = common_command + sku_args
     proc = common.Run(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     out, err = proc.communicate()
+    last_out_line = out.split()[-1] if out != "" else out
     if proc.returncode == 0:
       logger.info("Command `%s` returns 'compatible'", ' '.join(command))
-    elif out.strip() == "INCOMPATIBLE":
+    elif last_out_line.strip() == "INCOMPATIBLE":
       logger.info("Command `%s` returns 'incompatible'", ' '.join(command))
       success = False
     else: