* config/rs6000/sysv4.h (SUBTARGET_SWITCHES): Add -mwindiss.
(LINK_START_SPEC): Handle it.
(LINK_OS_SPEC): Likewise.
(CPP_SPEC): Likewise.
(STARTFILE_SPEC): Likewise.
(LIB_SPEC): Likewise.
(ENDFILE_SPEC): Likewise. Do not assume crtsavres.o is used on
all platforms.
(CRTSAVRES_DEFAULT_SPEC): New macro.
(LIB_WINDISS_SPEC): New macro.
(CPP_OS_WINDISS_SPEC): Likewise.
(STARTFILE_WINDISS_SPEC): Likewise.
(ENDFILE_WINDISS_SPEC): Likewise.
(LINK_START_WINDISS_SPEC): Likewise.
(LINK_OS_WINDISS_SPEC): Likewise.
* config/rs6000/windiss.h: New file.