Take the Unshadow stackguard from environment (#16583)

* try to take the stackguard depth for pushShadowedLocals from the environment

* add release notes entry

* add PR number

Author: dawedawe

docs/release-notes/.FSharp.Compiler.Service/8.0.300.md

@@ -6,6 +6,7 @@
 
 ### Added
 
+* The stackguard depth for ILPdbWriter.unshadowScopes can be modified via the environment variable `FSHARP_ILPdb_UnshadowScopes_StackGuardDepth`([PR #16583](https://github.com/dotnet/fsharp/pull/16583)) 
 * Parser recovers on complex primary constructor patterns, better tree representation for primary constructor patterns. ([PR #16425](https://github.com/dotnet/fsharp/pull/16425))
 * Name resolution: keep type vars in subsequent checks ([PR #16456](https://github.com/dotnet/fsharp/pull/16456))
 * Higher-order-function-based API for working with the untyped abstract syntax tree. ([PR #16462](https://github.com/dotnet/fsharp/pull/16462))

src/Compiler/AbstractIL/ilwritepdb.fs

@@ -16,6 +16,7 @@ open Internal.Utilities
 open FSharp.Compiler.AbstractIL.IL
 open FSharp.Compiler.AbstractIL.Support
 open Internal.Utilities.Library
+open Internal.Utilities.Library.Extras
 open FSharp.Compiler.DiagnosticsLogger
 open FSharp.Compiler.IO
 open FSharp.Compiler.Text.Range
@@ -1028,6 +1029,11 @@ let rec pushShadowedLocals (stackGuard: StackGuard) (localsToPush: PdbLocalVar[]
 //     adding the text " (shadowed)" to the names of those with name conflicts.
 let unshadowScopes rootScope =
     // Avoid stack overflow when writing linearly nested scopes
-    let stackGuard = StackGuard(100, "ILPdbWriter.unshadowScopes")
+    let UnshadowScopesStackGuardDepth =
+        GetEnvInteger "FSHARP_ILPdb_UnshadowScopes_StackGuardDepth" 100
+
+    let stackGuard =
+        StackGuard(UnshadowScopesStackGuardDepth, "ILPdbWriter.unshadowScopes")
+
     let result, _ = pushShadowedLocals stackGuard [||] rootScope
     result