ruby: remove references to XBPS_WRAPPERDIR in rbconfig.rb.

Fixes building external gems, as reported by arete74 on irc.

srcpkgs/ruby/template

@@ -3,7 +3,7 @@ _ruby_abiver=2.2.0
 
 pkgname=ruby
 version=2.2.2
-revision=1
+revision=2
 build_style=gnu-configure
 configure_args="--enable-shared --disable-rpath
  DOXYGEN=/usr/bin/doxygen DOT=/usr/bin/dot PKG_CONFIG=/usr/bin/pkg-config"
@@ -32,6 +32,9 @@ post_install() {
 	if [ "$CROSS_BUILD" ]; then
 		sed -e "s,${XBPS_CROSS_TRIPLET}-,,g" -i ${DESTDIR}/usr/lib/ruby/${_ruby_abiver}/*/rbconfig.rb
 	fi
+	# Replace reference to the install(1) wrapper
+	sed -e "s,${XBPS_WRAPPERDIR},/usr/bin,g" -i \
+		${DESTDIR}/usr/lib/ruby/${_ruby_abiver}/*/rbconfig.rb
 }
 
 ruby-devel-docs_package() {