Fix outdated build instructions in compiling docs (#58)

- Remove confusing 'copy {path_to_osx_update}' command from Release/Build section
- Add clear per-platform build instructions for Windows, OSX, and Linux
- Separate local dev builds from cross-platform production builds
- Add links to Avalonia sample dev-scripts and CI workflows
- Update prerequisites to .NET 8 SDK (removed .NET 6)
- Fix incorrect 'src/Rust' reference to 'src/bins' in Linux section
- Add OSX/Linux commands to Debug/Test section
- Update Linux dotnet-install to only install .NET 8

Fixes #35

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Keboo

docs/contributing/compiling.mdx

@@ -10,15 +10,15 @@ It is made up of:
 In order to test the project, you need to build the Rust binaries before compiling dotnet.   
 
 ### Prerequisites
- - [.NET 6 SDK](https://dotnet.microsoft.com/download/dotnet/6.0)
  - [.NET 8 SDK](https://dotnet.microsoft.com/download/dotnet/8.0)
  - [Rust / Cargo](https://www.rust-lang.org/tools/install)
  - `dotnet tool install -g dotnet-coverage`
  - `dotnet tool install -g nbgv`
 
 ### Debug / Test
-On windows, you need to build the Rust binaries using the `windows` feature before running tests. On OSX, you should run `cargo build` instead. 
+On Windows, you need to build the Rust binaries using the `windows` feature before running tests. On OSX or Linux, you should run `cargo build` without the feature flag instead. 
 
+On Windows:
 ```shell
 git clone https://github.com/velopack/velopack.git
 cd velopack/src/bins
@@ -28,25 +28,56 @@ dotnet build
 dotnet test --no-build
 ```
 
+On OSX / Linux:
+```shell
+git clone https://github.com/velopack/velopack.git
+cd velopack/src/bins
+cargo build
+cd ../../
+dotnet build
+dotnet test --no-build
+```
+
 ### Release / Build
-This is slightly complicated, because you will need to compile Rust on x64 OSX and x64 Windows before creating the final packages.
+Creating a full production release is complex because Velopack must include native binaries for Windows, Linux, and macOS. You need to build the Rust binaries separately on each platform, then combine them on the final build machine using `/p:PackRustAssets=true`.
+
+For **local development**, you typically only need binaries for your current OS. The simplest approach is:
+
+On Windows:
+```shell
+git clone https://github.com/velopack/velopack.git
+cd velopack/src/bins
+cargo build --release --features windows
+cd ../../
+dotnet build -c Release
+```
 
 On OSX:
 ```shell
 git clone https://github.com/velopack/velopack.git
 cd velopack/src/bins
 cargo build --release
+cd ../../
+dotnet build -c Release
 ```
 
-On Windows:
+On Linux:
 ```shell
 git clone https://github.com/velopack/velopack.git
 cd velopack/src/bins
-cargo build --release --features windows
-copy {path_to_osx_update} target/release/updatemac
-dotnet build -c Release /p:PackRustAssets=true
+cargo build --release
+cd ../../
+dotnet build -c Release
 ```
 
+:::tip
+For a complete working example of building a release using local Velopack code, see the [dev-scripts in the Avalonia sample](https://github.com/velopack/velopack/tree/master/samples/CSharpAvalonia/dev-scripts).
+:::
+
+:::note
+A full **cross-platform production build** (combining binaries from all operating systems into one package) requires building Rust on each platform first, then running `dotnet build -c Release /p:PackRustAssets=true` with all platform binaries present. This workflow is handled by CI and is not practical to replicate locally. See the [CI workflows](https://github.com/velopack/velopack/tree/master/.github/workflows) for details.
+:::
+
 ### Preparing Linux
 If you are on Linux (tested on Ubuntu), there are additional package pre-requisites:
 ```shell
@@ -56,7 +87,6 @@ sudo apt install libssl-dev pkg-config build-essential
 Installing dotnet and setting up the paths are a pain, I recommend using the [dotnet-install.sh](https://learn.microsoft.com/dotnet/core/tools/dotnet-install-script) script.
 
 ```shell
-./dotnet-install.sh -c 6.0
 ./dotnet-install.sh -c 8.0
 ```
 
@@ -82,7 +112,7 @@ dotnet could be at a different location (eg. `/usr/share/dotnet`) and the paths
 
 Once dotnet is configured, you can Install Rust, typically done with the [rustup script available here](https://www.rust-lang.org/tools/install)
 
-To verify that Rust is installed and working correctly, you should compile the Rust binaries in `src/Rust`:
+To verify that Rust is installed and working correctly, you should compile the Rust binaries in `src/bins`:
 
 ```shell
 cargo build --target x86_64-unknown-linux-gnu --release