Fix cdex bugs to enable ART_DEFAULT_COMPACT_DEX_LEVEL=fast tests passing

Compute dex checksum for compact dex generation. Handle input vdex
by not aborting in oat_writer, instead just avoid generating compact
dex for the input vdex case.

Re-enabled some compact dex tests.

Bug: 63756964
Test: ART_DEFAULT_COMPACT_DEX_LEVEL=fast test-art-host
Change-Id: Ic9b4e4e59e6cd22b66ee2fc0d32c9b4a15f13497
diff --git a/test/knownfailures.json b/test/knownfailures.json
index ae1830a..dc051d9 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -383,7 +383,7 @@
         "tests": ["629-vdex-speed",
                   "634-vdex-duplicate"],
         "description": ["Profile driven dexlayout does not work with vdex or dex verifier."],
-        "variant": "speed-profile | cdex-fast"
+        "variant": "speed-profile"
     },
     {
         "test_patterns": ["616-cha.*"],
@@ -651,9 +651,9 @@
         "description": ["Test is designed to only check --compiler-filter=speed"]
     },
     {
-        "tests": ["628-vdex", "975-iface-private"],
+        "tests": ["975-iface-private"],
         "variant": "cdex-fast",
-        "description": ["CompactDex doesn't yet work with input-vdex or 975-iface private"]
+        "description": ["CompactDex doesn't yet work with 975-iface private"]
     }
 
 ]