fix(build): improve cross-platform compatibility

- Add shebang to build.sh for proper shell execution
- Remove Windows-style line endings from build.sh
- Skip net462 tests on non-Windows platforms in TestTask.cs

These changes ensure the build system works correctly across different
operating systems by providing proper shell script execution headers
and preventing framework-specific tests from running on incompatible
platforms.

Author: Blind-Striker

build.sh

@@ -1,2 +1,4 @@
+#!/bin/bash
+
 dotnet build ./build/LocalStack.Build/LocalStack.Build.csproj > /dev/null 2>&1
 dotnet run --project ./build/LocalStack.Build/LocalStack.Build.csproj --no-launch-profile --no-build -- "$@"

build/LocalStack.Build/CakeTasks/TestTask.cs

@@ -54,13 +54,10 @@ public override void Run(BuildContext context)
                     }
                 }
 
-                // .NET Framework testing on non-Windows platforms
-                // - Modern .NET includes built-in Mono runtime
-                // - Test platform still requires external Mono installation on Linux
                 if (targetFramework == "net462" && !context.IsRunningOnWindows())
                 {
-                    string platform = context.IsRunningOnLinux() ? "Linux (with external Mono)" : "macOS (built-in Mono)";
-                    context.Information($"Running .NET Framework tests on {platform}");
+                    context.Warning("Skipping net462 tests on non-Windows platform");
+                    continue;
                 }
 
                 string testFilePrefix = targetFramework.Replace('.', '-');