[clang] [clang] Enforce 1-based indexing for command line source locations (PR #139457)

[Fangrui Song via cfe-commits]

================
@@ -0,0 +1,12 @@
+// Related to #139375
----------------
MaskRay wrote:

I don't why some regression tests are named `crash-*`, but I would not name this `crash-*`.

I'd just name this source-loc-zero.cpp and change this comment to `// Regression test for #139375`

https://github.com/llvm/llvm-project/pull/139457