(gdb_compile_shlib): Likewise.
(skip_shlib_tests, gdb_download, gdb_load_shlibs): New.
(default_gdb_init): Clear cleanfiles.
(gdb_finish): Delete recorded cleanfiles.
* lib/gdbserver-support.exp (gdbserver_spawn): Use gdb_download.
* gdb.base/gdb1555.exp: Use skip_shlib_tests and gdb_load_shlibs.
Do not use isnative.
* gdb.base/pending.exp, gdb.base/shlib-call.exp, gdb.base/shreloc.exp,
gdb.base/so-impl-ld.exp: Likewise.
* gdb.base/solib-weak.exp: Likewise. Skip for DLL targets.
* gdb.base/unload.exp: Likewise. Do not pass empty option to
gdb_compile.
