re PR lto/47225 (cross-compile fails while configuring libgcc with "xgcc: fatal error: -fuse-linker-plugin, but liblto_plugin.so not found")

ChangeLog:
PR lto/47225
* Makefile.def (lto-plugin): Double dash for enable-shared.
(configure-gcc): Depend on all-lto-plugin.
* Makefile.in: Rebuilt.
lto-plugin/ChangeLog:
PR lto/47225
* Makefile.am (gcc_build_dir, in_gcc_libs): New.
(liblto_plugin_la_LDFLAGS): Add -module.
(copy_lto_plugin): Renamed to...
($(in_gcc_libs)): ... this.  Add mkinstalldirs.  Skip copying
of static modules.
* Makefile.in: Rebuild.
gcc/ChangeLog:
PR lto/47225
* configure.ac (gcc_cv_lto_plugin): Test for liblto_plugin.la
in the current directory.
* configure: Rebuilt.

From-SVN: r170070