[clang] [clang][SourceManager] Use `getFileLoc` when computing `getPresumedLoc` (PR #166255)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-4` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/31102

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: Preprocessor/print_line_track.c' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/clang -cc1 -internal-isystem /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/lib/clang/22/include -nostdsysteminc -E /Users/buildbot/buildbot-root/llvm-project/clang/test/Preprocessor/print_line_track.c | grep -z 'a.3'
# executed command: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/clang -cc1 -internal-isystem /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/lib/clang/22/include -nostdsysteminc -E /Users/buildbot/buildbot-root/llvm-project/clang/test/Preprocessor/print_line_track.c
# note: command had no output on stdout or stderr
# executed command: grep -z a.3
# note: command had no output on stdout or stderr
# error: command failed with exit status: 1

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/166255