[vold] Add argument verification to IncFS methods

+ Get rid of an extra string copy in path validation function

Bug: 152349257
Test: atest vold_tests
Change-Id: I03a8cab0dd6abd7d5c9dcbbc2acb651e818e6cd8
diff --git a/Android.bp b/Android.bp
index c2f8936..03dde1e 100644
--- a/Android.bp
+++ b/Android.bp
@@ -131,6 +131,7 @@
         "ScryptParameters.cpp",
         "Utils.cpp",
         "VoldNativeService.cpp",
+        "VoldNativeServiceValidation.cpp",
         "VoldUtil.cpp",
         "VolumeManager.cpp",
         "cryptfs.cpp",