Make ClangSharpPInvokeGenerator --version output native library versions

[FiniteReality]

Rationale: It's a pain to specify a bunch of parameters just to check that I've got the project set up correctly.

For example, I'm trying to diagnose a few issues loading the utility library, and I'm getting this in the output:

~/Development/ClangSharp$ dotnet run --project sources/ClangSharpPInvokeGenerator/ClangSharpPInvokeGenerator.csproj --runtime debian.10-x64 --framework netcoreapp3.1 -- -f ../thermite/natives/minimp3/minimp3.h -l test -n test -o ../test.cs
Unhandled exception: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.DllNotFoundException: Unable to load shared library 'libClangSharp' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: liblibClangSharp: cannot open shared object file: No such file or directory
   at ClangSharp.Interop.clangsharp.Cursor_getDeclKind(CXCursor C)
   at ClangSharp.Interop.CXCursor.get_DeclKind() in /home/dev/Development/ClangSharp/sources/ClangSharp/Interop.Extensions/CXCursor.cs:line 56
// ... and the rest of the stack trace, trimmed for clarity

Being able to run something as simple as --version would be incredibly helpful without having to ensure my paths and filenames are 100% correct every time I invoke the tool. It'd also be more useful as a complete "test" to ensure that the tool has been built correctly (which it clearly isn't in my case).

[tannergooding]

@FiniteReality, the tooling now runs explicit logic to validate the loaded library version is as expected (https://github.com/microsoft/ClangSharp/blob/main/sources/ClangSharp.PInvokeGenerator/PInvokeGenerator.cs#L58-L70):

            var clangVersion = clang.getClangVersion().ToString();

            if (!clangVersion.Contains("13.0.0"))
            {
                throw new InvalidOperationException($"Invalid libClang version. Returned string '{clangVersion}' does not contain '{ExpectedClangVersion}'");
            }

            var clangSharpVersion = clangsharp.getVersion().ToString();

            if (!clangSharpVersion.Contains("13.0.0"))
            {
                throw new InvalidOperationException($"Invalid libClang version. Returned string '{clangSharpVersion}' does not contain '{ExpectedClangSharpVersion}'");
            }

Outside of this, there isn't much that can be done as DllNotFoundException is handled internally by the runtime interop handling; so this is a matter of it not finding libClangSharp in the first place. Setting LD_DEBUG would be the right way to determine what paths where being searched for libClangSharp in this scenario (as .NET and ClangSharp simply use the system default).

[FiniteReality]

Yeah. The idea was that I could use ClangSharpPInvokeGenerator --version to check that it can find and load the libraries without having it try to do any actual work.

[tannergooding]

Ah, I see. That should be trivial enough to add given that its validating things on the normal path now.