Detect Linux arm

Author: dellis1972

build/Build.csproj

@@ -22,6 +22,7 @@
     <Using Include="Cake.Core.Diagnostics" />
     <Using Include="Cake.Core.IO" />
     <Using Include="Cake.FileHelpers" />
+    <Using Include="System.Runtime.InteropServices" />
   </ItemGroup>
 
   <ItemGroup>

build/BuildLinuxTask.cs

@@ -9,7 +9,7 @@ public sealed class BuildLinuxTask : FrostingTask<BuildContext>
 
     public override void Run(BuildContext context)
     {
-        Architecture arch = RuntimeInformation.OSArchitecture;
+        var arch = RuntimeInformation.OSArchitecture;
         // Absolute path to the artifact directory is needed for flags since they don't allow relative path
         var artifactDir = context.MakeAbsolute(new DirectoryPath(context.ArtifactsDir));
         var dependencyDir = context.MakeAbsolute(new DirectoryPath($"{context.ArtifactsDir}/../dependencies-linux-{(arch == Architecture.Arm64 ? "arm64" : "x64")}"));
@@ -84,7 +84,7 @@ private static string GetFFMpegConfigureFlags(BuildContext context)
     {
         var ignoreCommentsAndNewLines = (string line) => !string.IsNullOrWhiteSpace(line) && !line.StartsWith('#');
         var configureFlags = context.FileReadLines("ffmpeg.config").Where(ignoreCommentsAndNewLines);
-        var osConfigFile = arch == Architecture.Arm64 ? "ffmpeg.linux-arm64.config" : "ffmpeg.linux-x64.config";
+        var osConfigFile = RuntimeInformation.OSArchitecture == Architecture.Arm64 ? "ffmpeg.linux-arm64.config" : "ffmpeg.linux-x64.config";
         var osConfigureFlags = context.FileReadLines(osConfigFile).Where(ignoreCommentsAndNewLines);
         return string.Join(' ', configureFlags) + " " + string.Join(' ', osConfigureFlags);
     }