GitHubCI: set DOTNET_ROLL_FORWARD=major for fsxc

Otherwise we would get this error (because the version of
fsxc that we're using was built with net6.x):

```
dotnet fsxc ./scripts/bump.fsx
You must install or update .NET to run this application.

App: D:\a\geewallet\geewallet\packages\fsxc\0.5.9.1\tools\net6.0\any\fsxc.dll
Architecture: x64
Framework: 'Microsoft.NETCore.App', version '6.0.0' (x64)
.NET location: C:\Program Files\dotnet\

The following frameworks were found:
  8.0.6 at [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  8.0.21 at [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  8.0.22 at [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  9.0.6 at [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  9.0.10 at [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  10.0.0 at [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]

The following frameworks for other architectures were found:
  x86
    8.0.21 at [C:\Program Files (x86)\dotnet\shared\Microsoft.NETCore.App]
    9.0.10 at [C:\Program Files (x86)\dotnet\shared\Microsoft.NETCore.App]

Learn more:
https://aka.ms/dotnet/app-launch-failed

To install missing framework, download:
https://aka.ms/dotnet-core-applaunch?framework=Microsoft.NETCore.App&framework_version=6.0.0&arch=x64&rid=win-x64&os=win10
```

Author: knocte

.github/workflows/CI.yml

@@ -60,7 +60,10 @@ jobs:
         # we need to install specific version because of this bug: https://github.com/dotnet/sdk/issues/24037
         dotnet tool install fsxc --version 0.5.9.1
 
-        find . -type f -name "*.fsx" | xargs -t -I {} dotnet fsxc {}
+        # fsxc was built with .NET6.x
+        export DOTNET_ROLL_FORWARD=major
+
+        find . -type f -name "*.fsx" | xargs -t -I {} fsxc {}
 
   macOS--mono-only:
     runs-on: macOS-13
@@ -155,7 +158,10 @@ jobs:
         # we need to install specific version because of this bug: https://github.com/dotnet/sdk/issues/24037
         dotnet tool install fsxc --version 0.5.9.1
 
-        find . -type f -name "*.fsx" | xargs -t -I {} dotnet fsxc {}
+        # fsxc was built with .NET6.x
+        export DOTNET_ROLL_FORWARD=major
+
+        find . -type f -name "*.fsx" | xargs -t -I {} fsxc {}
 
   windows--legacyFramework-only:
     runs-on: windows-2022
@@ -214,7 +220,10 @@ jobs:
         # we need to install specific version because of this bug: https://github.com/dotnet/sdk/issues/24037
         dotnet tool install fsxc --version 0.5.9.1
 
-        find . -type f -name "*.fsx" | xargs -t -I {} dotnet fsxc {}
+        # fsxc was built with .NET6.x
+        export DOTNET_ROLL_FORWARD=major
+
+        find . -type f -name "*.fsx" | xargs -t -I {} fsxc {}
 
   linux24-github--dotnet-and-mono:
     runs-on: ubuntu-24.04
@@ -344,7 +353,10 @@ jobs:
         # we need to install specific version because of this bug: https://github.com/dotnet/sdk/issues/24037
         dotnet tool install fsxc --version 0.5.9.1
 
-        find . -type f -name "*.fsx" | xargs -t -I {} dotnet fsxc {}
+        # fsxc was built with .NET6.x
+        export DOTNET_ROLL_FORWARD=major
+
+        find . -type f -name "*.fsx" | xargs -t -I {} fsxc {}
 
   linux24-vanilla--stockdotnet-and-newmono:
     runs-on: ubuntu-24.04
@@ -388,7 +400,10 @@ jobs:
         # we need to install specific version because of this bug: https://github.com/dotnet/sdk/issues/24037
         dotnet tool install fsxc --version 0.5.9.1
 
-        find . -type f -name "*.fsx" | xargs -t -I {} dotnet fsxc {}
+        # fsxc was built with .NET6.x
+        export DOTNET_ROLL_FORWARD=major
+
+        find . -type f -name "*.fsx" | xargs -t -I {} fsxc {}
 
   linux24-vanilla--stockdotnet-and-stockmono:
     runs-on: ubuntu-24.04
@@ -430,7 +445,10 @@ jobs:
         # we need to install specific version because of this bug: https://github.com/dotnet/sdk/issues/24037
         dotnet tool install fsxc --version 0.5.9.1
 
-        find . -type f -name "*.fsx" | xargs -t -I {} dotnet fsxc {}
+        # fsxc was built with .NET6.x
+        export DOTNET_ROLL_FORWARD=major
+
+        find . -type f -name "*.fsx" | xargs -t -I {} fsxc {}
 
   linux24-vanilla--newmono-only:
     runs-on: ubuntu-24.04