[llvm] [llvm/CAS] Improve layering and decouple `UnifiedOnDiskCache` from the builtin hash implementation (PR #177280)

[Nico Weber via llvm-commits]

================
@@ -42,25 +42,29 @@ static Expected<size_t> countFileSizes(StringRef Path) {
   return TotalSize;
 }
 
-TEST_F(OnDiskCASTest, UnifiedOnDiskCacheTest) {
+TEST_P(CustomHasherOnDiskCASTest, UnifiedOnDiskCacheTest) {
----------------
nico wrote:

@akyrtzi Ping.

https://github.com/llvm/llvm-project/pull/177280