Include the major version when referencing *.so libraries

Describe the bug

Linux distributions typically split libraries like libgpiod into multiple packages.

One specific split is between libgpiod and libgpiod-dev, where the former contains the necessary binaries and symlinks to run programs while the latter is meant for development, where you (traditionally) invoke a linker to produce a binary. The latter typically uses the unversioned symlink to simplify the build and the binary referencing the library then includes the versioned reference. In this split, the full version (libgpiod.so.2.1.3) and a symlink with the major version (libgpiod.so.2) are in the main package, the unversioned symlink (libgpiod.so) is in the -dev package, which doesn’t get installed per default.

For example for Ubuntu:

• https://packages.ubuntu.com/bionic/amd64/libgpiod1/filelist
• https://packages.ubuntu.com/bionic/amd64/libgpiod-dev/filelist

Embedded distributions like Yocto per default do not install the -dev package into the image when you declare a runtime dependency on a library. Including the -dev package in the image can have unwanted side-effects of pulling in other development dependencies (for example I ended up with a Python interpreter in my image for a different -dev package in the past)

My own Yocto image doesn’t include any -dev packages, so in order to use the LibGpiodDriver in my code, I have to “translate” the DllImport string by

static MyType()
    => NativeLibrary.SetDllImportResolver(typeof(GpioDriver).Assembly, libgpiodFixup);

private static IntPtr libgpiodFixup(string libraryName, Assembly assembly, DllImportSearchPath? searchPath)
{
    if (libraryName == "libgpiod")
        if (NativeLibrary.TryLoad("libgpiod.so.2", assembly, searchPath, out var result))
            return result;
    return IntPtr.Zero;
}

However, this “trick” only works exactly once per assembly (only one resolver per assembly), and the NativeLibrary API is meant to be used within the library requiring a specialized resolver. If System.Device.Gpio would decide to start using that functionality in the future, my own fixup would be broken.

Since the C# interop code typically relies on a specific major ABI version when declaring methods from an external library like libgpiod, that major version should be included in the DllImport instead of the unversioned .so.

Steps to reproduce

Run code using LibGpiodDriver on a Linux image without the libgpiod-dev package.

Expected behavior Run without exception.

Actual behavior DllNotFoundException

Versions used

Add following information:

• dotnet --info on the machine being used to build

.NET Core SDK (reflecting any global.json):
 Version:   3.1.101
 Commit:    b377529961

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  18.04
 OS Platform: Linux
 RID:         ubuntu.18.04-x64
 Base Path:   /usr/share/dotnet/sdk/3.1.101/

Host (useful for support):
  Version: 3.1.1
  Commit:  a1388f194c

.NET Core SDKs installed:
  2.2.402 [/usr/share/dotnet/sdk]
  3.0.102 [/usr/share/dotnet/sdk]
  3.1.101 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.2.8 [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.2.8 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.2 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.1 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.2.8 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.2 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.1 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

• dotnet --info on the machine where app is being run

  It was not possible to find any installed .NET Core SDKs
  Did you mean to run .NET Core SDK commands? Install a .NET Core SDK from:
      https://aka.ms/dotnet-download

Host (useful for support):
  Version: 3.1.3
  Commit:  4a9f85e9f8

.NET Core SDKs installed:
  No SDKs were found.

.NET Core runtimes installed:
  Microsoft.AspNetCore.App 3.1.3 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.1.3 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

• Version of System.Device.Gpio package: 1.0.0

[joperezr]

I see, yeah I think depending on the major version seems reasonable to me.

[krwq]

[Triage] If we fix this libgpiod can be used without installing dev package. Bumping priority.