[clang] [clang][Analyzer] Move checker 'alpha.unix.Errno' to 'unix.Errno'. (PR #69469)

[Balázs Kéri via cfe-commits]

balazske wrote:

> I also think that the [reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/report-detail?run=postgres_REL_13_0_errno_alpha_unix&newcheck=postgres_REL_13_0_errno_unix&is-unique=on&diff-type=New&report-id=3253666&report-hash=b4e0b723164236269fe6078ad32a0456&report-filepath=%2apg_basebackup.c) [from](https://codechecker-demo.eastus.cloudapp.azure.com/Default/report-detail?run=postgres_REL_13_0_errno_alpha_unix&newcheck=postgres_REL_13_0_errno_unix&is-unique=on&diff-type=New&report-id=3254052&report-hash=619eb5d998324adb5e02d9e3302bb4d5&report-filepath=%2acopy.c) [postgres](https://codechecker-demo.eastus.cloudapp.azure.com/Default/report-detail?run=postgres_REL_13_0_errno_alpha_unix&newcheck=postgres_REL_13_0_errno_unix&is-unique=on&diff-type=New&report-id=3256373&report-hash=32f8e213c6fb419277ec76c40bfa3956&report-filepath=%2afe-connect.c) that you mentioned are too confusing.
> 

After the change in #71392 the report looks like [this](https://codechecker-demo.eastus.cloudapp.azure.com/Default/report-detail?run=postgres_REL_13_0_test_71392_base&newcheck=postgres_REL_13_0_test_71392&is-unique=on&diff-type=Unresolved&checker-name=alpha.unix.Errno&report-hash=0b2d4e61a48cd556bb982b39969b81d2&report-id=3386353&report-filepath=%2acopy.c). This looks somewhat better, probably still false positive because the "len" can not be 0, but the checker does not have more information.

https://github.com/llvm/llvm-project/pull/69469