X86: remove ldso-stubs.S from more configs

Group 1. These ports were tested on qemu-system-i386:

* netbsd: worked fine on release 6.6 (also, don't need "undefineds.c")
* openbsd: worked fine using release 9.0
* opensolaris: C toolchain default is to produce 32-bit code, which worked.
  (I didn't notice that the default was 32-bit until I further observed that
   "-m64" in Config.x86-64-sunos is required to produce a 64-bit executable)

Group 2. Ports in indeterminate state.
These may work for some very old OS release, or not work,
but either way it should have nothing to do with ldso-stubs:

* dragonfly: home page says "DragonFly BSD is 64-bit only."
  (was not sure where to obtain older releases)
* gnu-kfreebsd: did not test,
  probably works but project is no longer maintained
* macOS: toolchain prints that 32-bit code is deprecated,
  and by "deprecated" it means "totally broken"

src/runtime/Config.x86-darwin

@@ -42,7 +42,7 @@ ifdef LISP_FEATURE_SB_LINKABLE_RUNTIME
   USE_LIBSBCL = -Wl,-force_load libsbcl.a
 endif
 
-ASSEM_SRC = x86-assem.S ldso-stubs.S
+ASSEM_SRC = x86-assem.S
 ARCH_SRC = x86-arch.c
 
 CPPFLAGS += -no-cpp-precomp

src/runtime/Config.x86-dragonfly

@@ -13,7 +13,6 @@
 
 include Config.x86-bsd
 
-ASSEM_SRC += ldso-stubs.S
 LINKFLAGS += -dynamic -export-dynamic
 # Link against pthread even if we do not want threaded SBCL
 # This is because of bug in DragonFly RTLD which sometimes

src/runtime/Config.x86-gnu-kfreebsd

@@ -11,8 +11,6 @@
 
 include Config.x86-bsd
 
-ASSEM_SRC += ldso-stubs.S
-
 # Until sbcl-0.6.7.3, we used "LINKFLAGS+=-static" here, which
 # worked fine for most things, but LOAD-FOREIGN & friends require
 # dlopen() etc., which in turn depend on dynamic linking of the

src/runtime/Config.x86-netbsd

@@ -11,8 +11,6 @@
 
 include Config.x86-bsd
 
-ASSEM_SRC += ldso-stubs.S
-OS_SRC += undefineds.c
 LINKFLAGS += -dynamic -export-dynamic
 
 CFLAGS = -g -Wall -O2 -fno-omit-frame-pointer

src/runtime/Config.x86-openbsd

@@ -12,8 +12,6 @@
 include Config.x86-bsd
 include Config.generic-openbsd
 
-ASSEM_SRC += ldso-stubs.S
-
 # The -Z linker flag conflicts with the default address space
 # locations used. If you wish to link the runtime using -Z option then
 # please see the comments in src/compiler/x86/parms.lisp

src/runtime/Config.x86-sunos

@@ -14,7 +14,7 @@ CFLAGS = -g -O2 -Wall -D__EXTENSIONS__ -D_POSIX_C_SOURCE=199506L -DSVR4 -D_REENT
 NM = nm -xgp
 GREP = ggrep
 
-ASSEM_SRC = x86-assem.S ldso-stubs.S
+ASSEM_SRC = x86-assem.S
 ARCH_SRC = x86-arch.c
 
 OS_SRC = sunos-os.c x86-sunos-os.c