mklibgcc.in: Build shared libgcc and shared libunwind in gcc/.

	* mklibgcc.in: Build shared libgcc and shared libunwind in gcc/.
	Don't subst shlib_dir for SHLIB_LINK, SHLIBUNWIND_LINK,
	SHLIB_INSTALL, and SHLIBUNWIND_INSTALL.
	* config/i386/t-nwld (SHLIB_NAME): Use shlib_base_name in place of
	shlib_dir and shlib_so_name.
	* config/mips/t-slibgcc-irix (SHLIB_NAME): Likewise.
	* config/t-libunwind-elf (SHLIB_NAME): Likewise.
	* config/t-slibgcc-darwin (SHLIB_NAME): Likewise.
	* config/t-slibgcc-elf-ver (SHLIB_NAME): Likewise.
	* config/t-slibgcc-sld (SHLIB_NAME): Likewise.
	(SHLIB_LINK): Don't use shlib_dir when creating symlink.

From-SVN: r91724