[Truffle] Add Process.gid=

Author: bjfish

truffle/src/main/java/org/jruby/truffle/nodes/rubinius/PosixNodes.java

@@ -351,6 +351,20 @@ public int getpriority(int kind, int id) {
 
     }
 
+    @CoreMethod(names = "setgid", isModuleFunction = true, required = 1, lowerFixnumParameters = 0)
+    public abstract static class SetgidNode extends CoreMethodArrayArgumentsNode {
+
+        public SetgidNode(RubyContext context, SourceSection sourceSection) {
+            super(context, sourceSection);
+        }
+
+        @Specialization
+        public int setgid(int gid) {
+            return posix().setgid(gid);
+        }
+
+    }
+
     @CoreMethod(names = "setpriority", isModuleFunction = true, required = 3, lowerFixnumParameters = {0, 1, 2})
     public abstract static class SetPriorityNode extends CoreMethodArrayArgumentsNode {
 

truffle/src/main/ruby/core/rubinius/common/process.rb

@@ -130,6 +130,11 @@ def self.uid=(uid)
     uid
   end
 
+  def self.gid=(gid)
+    gid = Rubinius::Type.coerce_to gid, Integer, :to_int
+    Process::Sys.setgid gid
+  end
+
   def self.euid=(uid)
     # the 4 rescue clauses below are needed
     # until respond_to? can be used to query the implementation of methods attached via FFI