[clang] [llvm] Update documentation and release notes for llvm-profgen COFF support (PR #84864)

[Haohai Wen via llvm-commits]

================
@@ -2434,6 +2449,15 @@ usual build cycle when using sample profilers for optimization:
    it provides better call information, which improves the accuracy of
    the profile data.
 
+   When using SEP:
+
+   .. code-block:: console
+
+     $ sep -start -ec BR_INST_RETIRED.NEAR_TAKEN:precise=yes:pdir -lbr no_filter:usr -perf-script ip,brstack -app ./code
----------------
HaohaiWen wrote:

Should we add `-out code.tb7 to sep'? Otherwise sep will generate a temp name (tbs17644.perf.data.script in my env).
e.g.
```
sep -start -out code.tb7 -ec BR_INST_RETIRED.NEAR_TAKEN:precise=yes:pdir -lbr no_filter:usr -perf-script brstack -app ./code
```

https://github.com/llvm/llvm-project/pull/84864