When build != host, create libiberty for the build machine.

When build != host, create libiberty for the build machine.

* Makefile.in (TARGET_CONFIGARGS, BUILD_CONFIGARGS): Replace
CONFIG_ARGUMENTS.
(ALL_BUILD_MODULES_LIST, BUILD_CONFIGDIRS, BUILD_SUBDIR):
New variables.
(ALL_BUILD_MODULES, CONFIGURE_BUILD_MODULES): New variables
and rules.
(all.normal): Depend on ALL_BUILD_MODULES.
(CONFIGURE_TARGET_MODULES rule): Use TARGET_CONFIGARGS.
(all-build-libiberty): Depend on configure-build-libiberty.

* configure: Calculate and substitute proper value for
ALL_BUILD_MODULES.
* configure.in: Create the build subdirectory.
Calculate and substitute TARGET_CONFIGARGS (formerly
CONFIG_ARGUMENTS); also BUILD_SUBDIR and BUILD_CONFIGARGS (new).