C#: Add CodeQL extractor pack files

csharp/tools/linux64/extract-csharp.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+echo extract-csharp.sh: Called with arguments: "$@"
+
+extractor="$CODEQL_EXTRACTOR_CSHARP_ROOT/tools/$CODEQL_PLATFORM/Semmle.Extraction.CSharp.Driver"
+
+for i in "$@"
+do
+  shift
+  if [[ `basename -- "$i"` =~ csc.exe|mcs.exe|csc.dll ]]
+  then
+    echo extract-csharp.sh: exec $extractor --cil $@
+    exec "$extractor" --compiler $i --cil $@
+  fi
+done
+
+echo extract-csharp.sh: Not a compiler invocation