[GR-17097] Avoid NFI exception while loading libc via full FFI.

PullRequest: truffleruby/945

Author: eregon

lib/truffle/ffi.rb

@@ -27,6 +27,12 @@ module Platform
     # so we need to break the cycle.
     ADDRESS_SIZE = 64
     LONG_SIZE = 64
+
+    if ::Truffle::Platform.linux?
+      # Set it so FFI::Library finds the right file directly, like on MRI,
+      # and does not need to try and fail to load the /lib64/libc.so loader script.
+      GNU_LIBC = 'libc.so.6'
+    end
   end
 
   TypeDefs = {}

lib/truffle/socket/truffle/foreign.rb

@@ -28,7 +28,7 @@ module Truffle
   module Socket
     module Foreign
       extend ::FFI::Library
-      ffi_lib ::FFI::Library::LIBC
+      ffi_lib ::FFI::Library::CURRENT_PROCESS
 
       SIZEOF_INT = ::FFI.type_size(:int)