[llvm] [CAS] Add OnDiskGraphDB and OnDiskKeyValueDB (PR #114102)

[Steven Wu via llvm-commits]

cachemeifyoucan wrote:

I manage to build inside a container but I am not able to reproduce:
```
[  PASSED  ] 22 tests.
[root at 767c9162-505f-4e6b-ad0e-8218fd3e74dd build]#  cat /etc/redhat-release
Red Hat Enterprise Linux release 10.0 (Coughlan)
[root at 767c9162-505f-4e6b-ad0e-8218fd3e74dd build]# uname -a
Linux 767c9162-505f-4e6b-ad0e-8218fd3e74dd 6.6.9 #1 SMP Fri Sep  5 23:08:25 UTC 2025 aarch64 GNU/Linux
[root at 767c9162-505f-4e6b-ad0e-8218fd3e74dd build]# mount
/dev/vda on / type ext4 (rw,relatime)
```

https://github.com/llvm/llvm-project/pull/114102