[GR-29448] Do not link against libtruffleruby for C extensions

* So a built C extension can be reused from multiple builds if they have the same ABI.
* Ideally we would still link to libtruffleruby without a -rpath, but that
  needs support in Sulong to specify a libraryPath from Ruby when loading a C extension.

Author: eregon

lib/mri/mkmf.rb

@@ -2302,25 +2302,6 @@ def depend_rules(depend)
   # +VPATH+ and added to the list of +INCFLAGS+.
   #
   def create_makefile(target, srcprefix = nil)
-    if defined?(::TruffleRuby) and Truffle::Boot.get_option('building-core-cexts') and target != 'libtruffleruby'
-      # Replace the -rpath argument in $LIBRUBYARG with a relative path to libtruffleruby for core C exts
-      # Relative path from lib/mri/$TARGET to lib/cext/libtruffleruby.so
-      nesting = target.count('/')
-      target_dir_to_libtruffleruby_dir = "#{'../' * nesting}../cext"
-      if Truffle::Platform.darwin?
-        origin_token = '@loader_path'
-      else
-        origin_token = '$$ORIGIN' # $$ so the Makefile does not expand it
-      end
-
-      librubyarg = $LIBRUBYARG.split(' ')
-      rpath_index = librubyarg.index('-rpath')
-      raise 'Could not find -rpath in $LIBRUBYARG' unless rpath_index
-      # Extra quotes so the shell does not try to interpret $ORIGIN
-      librubyarg[rpath_index + 1] = "'#{origin_token}/#{target_dir_to_libtruffleruby_dir}'"
-      $LIBRUBYARG = librubyarg.join(' ')
-    end
-
     $target = target
     libpath = $DEFLIBPATH|$LIBPATH
     message "creating Makefile\n"
@@ -2839,6 +2820,12 @@ def MAIN_DOES_NOTHING(*refs)
     "$(CC) #{OUTFLAG}#{CONFTEST}#{$EXEEXT} $(INCFLAGS) $(CPPFLAGS) " \
     "$(CFLAGS) $(src) $(LIBPATH) $(LDFLAGS) $(ARCH_FLAG) $(LOCAL_LIBS) $(LIBS)"
 
+  if defined?(::TruffleRuby)
+    # We need to link to libtruffleruby for MakeMakefile#try_link to succeed
+    libtruffleruby_dir = File.dirname(RbConfig::CONFIG['libtruffleruby'])
+    TRY_LINK << " -L#{libtruffleruby_dir} -ltruffleruby"
+  end
+
   ##
   # Command which will link a shared library
 

lib/truffle/rbconfig.rb

@@ -126,9 +126,8 @@ module RbConfig
     dldflags << rpath_libcxx
   end
 
-  # Link to libtruffleruby by absolute path
-  libtruffleruby_dir = File.dirname(libtruffleruby)
-  librubyarg = "-L#{libtruffleruby_dir} -rpath #{libtruffleruby_dir} -ltruffleruby -lgraalvm-llvm"
+  # We do not link to libtruffleruby here to workaround GR-29448
+  librubyarg = '-lgraalvm-llvm'
 
   warnflags = warnflags.join(' ')
 
@@ -173,6 +172,7 @@ module RbConfig
     'LIBRUBYARG_STATIC' => '',
     'LIBRUBY_SO'        => "cext/libtruffleruby.#{Truffle::Platform::SOEXT}",
     'LIBS'              => libs,
+    'libtruffleruby'    => libtruffleruby,
     'NULLCMD'           => ':',
     'OBJEXT'            => 'o',
     'optflags'          => optflags,

src/main/c/cext/extconf.rb

@@ -23,15 +23,4 @@ module Truffle::Platform
 # -DRUBY_EXPORT is added in MRI's configure.in.
 $CFLAGS << " -DRUBY_EXPORT"
 
-# Do no link against libtruffleruby for libtruffleruby itself.
-# We still need libtruffleruby to link against libgraalvm-llvm,
-# otherwise linking fails with "Undefined symbols" on macOS.
-if Truffle::Platform.darwin?
-  # Set the install_name of libtruffleruby on macOS, so C exts linking to it
-  # will know they need to look at the rpath to find it.
-  $LIBRUBYARG = "-Wl,-install_name,@rpath/libtruffleruby.dylib -lgraalvm-llvm"
-else
-  $LIBRUBYARG = "-lgraalvm-llvm"
-end
-
 create_makefile('libtruffleruby')