Document baseline update and allow tests to run in debug mode without…

… assert (dotnet#8149)

* document baseline update and allow tests to run in debug mode without assert

* Update DEVGUIDE.md

* Update DEVGUIDE.md

* Update readme.md

src/fsharp/IlxGen.fs

@@ -5089,7 +5089,6 @@ and GenDecisionTreeSwitch cenv cgbuf inplabOpt stackAtTargets eenv e cases defau
             | _ -> error(InternalError("these matches should never be needed", switchm))
 
 and GenDecisionTreeCases cenv cgbuf stackAtTargets eenv defaultTargetOpt targets repeatSP targetInfos sequel caseLabels cases (contf: Zmap<_,_> -> FakeUnit) =
-    assert(cgbuf.GetCurrentStack() = stackAtTargets) // cgbuf stack should be unchanged over tests. [bug://1750].
 
     match defaultTargetOpt with
     | Some defaultTarget -> 

tests/fsharpqa/readme.md

@@ -32,3 +32,17 @@ A convenience "fsharpqafiles.csproj" project is located in the fsharp.sln soluti
 
 (TODO, provide some guidance about how to define env.lst files)
 
+## Updating baselines in tests
+
+Some tests use "baseline" files.  There is sometimes a way to update these baselines en-masse in your local build,
+useful when some change affects many baselines.  For example, in the 'fsharpqa' tests the baselines
+are updated using scripts or utilities that allow the following environment variable to be set:
+
+```
+set TEST_UPDATE_BSL=1
+```
+
+Updating baselines en-masse should be done very carefully and subject to careful code review.   Where possible the
+compiler change causing the en-masse update should be isolated and minimized so it is obvious at review time that no other
+code generation chagnes will be caused.
+

tests/fsharpqa/testenv/bin/runall.pl

@@ -147,7 +147,7 @@
 my $FILE_ERROR_EXITVAL = 5;
 my $OTHER_ERROR_EXITVAL = 9;
 
-my $perl = $Config{perlpath};
+my $perl = $^X;
 
 BEGIN {
     @required_mods = ("Win32\\Process.pm");