Fix directory separator character

Author: claudiamurialdo

.github/workflows/External-Storage-Tests.yml

@@ -56,7 +56,7 @@ jobs:
     - name: Create temporal solution with .NET 8 projects
       run: |
         dotnet new sln --name $SolutionFileName --output dotnet --force
-        dotnet msbuild dotnet\DotNetStandardClasses.sln /t:DumpProjectsAndTests -p:DumpSolutionName=$SolutionFileName /m:1 -p:DumpSolutionTargetFrameworkDefault=net8
+        dotnet msbuild dotnet/DotNetStandardClasses.sln /t:DumpProjectsAndTests -p:DumpSolutionName=$SolutionFileName /m:1 -p:DumpSolutionTargetFrameworkDefault=net8
 
     - name: Restore packages
       run: dotnet restore $SolutionFile