re PR target/40125 (libgcc_s DLL installed in wrong directory in cross toolchain)
gcc/ChangeLog:
PR target/40125
* config.gcc (i[34567]86-*-pe | i[34567]86-*-cygwin*): Select suitable
t-dlldir{,-x} fragment for build and add it to tmake_file.
(i[34567]86-*-mingw* | x86_64-*-mingw*): Likewise.
* Makefile.in (libgcc.mvars): Also export SHLIB_DLLDIR to libgcc.
* config/i386/t-dlldir: New file.
(SHLIB_DLLDIR): Define.
* config/i386/t-dlldir-x: New file.
(SHLIB_DLLDIR): Define.
* config/i386/t-cygming: Error out if SHLIB_DLLDIR is not set.
(SHLIB_INSTALL): Use it.