sparc/vdso: Always reject undefined references during linking

Instead of using a custom script to detect and fail on undefined
references, use --no-undefined for all VDSO linker invocations.

Drop the now unused checkundef.sh script.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andreas Larsson <andreas@gaisler.com>
Link: https://lore.kernel.org/r/20250306-vdso-checkundef-v2-2-a26cc315fd73@linutronix.de

arch/sparc/vdso/Makefile

@@ -22,7 +22,7 @@ targets += $(foreach x, 32 64, vdso-image-$(x).c vdso$(x).so vdso$(x).so.dbg)
 
 CPPFLAGS_vdso.lds += -P -C
 
-VDSO_LDFLAGS_vdso.lds = -m elf64_sparc -soname linux-vdso.so.1 --no-undefined \
+VDSO_LDFLAGS_vdso.lds = -m elf64_sparc -soname linux-vdso.so.1 \
 			-z max-page-size=8192
 
 $(obj)/vdso64.so.dbg: $(obj)/vdso.lds $(vobjs) FORCE
@@ -101,7 +101,6 @@ $(obj)/vdso32.so.dbg: FORCE \
 quiet_cmd_vdso = VDSO    $@
       cmd_vdso = $(LD) -nostdlib -o $@ \
 		       $(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
-		       -T $(filter %.lds,$^) $(filter %.o,$^) && \
-		sh $(src)/checkundef.sh '$(OBJDUMP)' '$@'
+		       -T $(filter %.lds,$^) $(filter %.o,$^)
 
-VDSO_LDFLAGS = -shared --hash-style=both --build-id=sha1 -Bsymbolic
+VDSO_LDFLAGS = -shared --hash-style=both --build-id=sha1 -Bsymbolic --no-undefined