[GR-18163] Set RbConfig::CONFIG LIBPATH and RPATHFLAG like CRuby

PullRequest: truffleruby/2422

Author: eregon

CHANGELOG.md

@@ -53,6 +53,7 @@ Compatibility:
 * Refinements take place at `Object#method` and `Module#instance_method` (#2004, @ssnickolay).
 * Add support for `rb_scan_args_kw` in C API (#2244, @LillianZ).
 * Update random implementation layout to be more compatible (#2234).
+* Set `RbConfig::CONFIG['LIBPATHFLAG'/'RPATHFLAG']` like MRI to let `$LIBPATH` changes in `extconf.rb` work.
 
 Performance:
 

lib/truffle/rbconfig.rb

@@ -165,6 +165,7 @@ module RbConfig
     'libdirname'        => 'libdir',
     'LIBEXT'            => 'a',
     'LIBPATHENV'        => 'LD_LIBRARY_PATH',
+    'LIBPATHFLAG'       => ' -L%1$-s',
     'LIBRUBY'           => '',
     'LIBRUBY_A'         => '',
     'LIBRUBYARG'        => librubyarg,
@@ -180,6 +181,7 @@ module RbConfig
     'prefix'            => prefix,
     'RANLIB'            => ranlib,
     'RM'                => 'rm -f',
+    'RPATHFLAG'         => ' -Wl,-rpath,%1$-s',
     'RUBY_BASE_NAME'    => ruby_base_name,
     'ruby_install_name' => ruby_install_name,
     'RUBY_INSTALL_NAME' => ruby_install_name,