ld: sframe: do not generate .sframe for PLT if no .sframe is in input BFDs

GNU ld creates SFrame stack trace info for the PLT. For x86 the linker-
created .sframe section is created in setup_gnu_properties.  For s390 it
is created in create_dynamic_sections.  For both, the section data is
itself emitted a bit later in late_size_sections.  Note that for aarch64 the
linker does not create .sframe for PLT yet.

Recall that a previous patch disentangled --no-ld-generated-unwind-info
from the linker-generated .sframe sections: this means that the linker
now generates .sframe section (for .plt*) for the first input BFD
enthusiatically even when none of the input BFDs have any .sframe
section, unless --discard-sframe is also added.  The issue is that these
(unexpected) linker-generated .sframe sections (on x86_64, and s390) may
now trip the linking process, e.g., when using --orphan-handling=error
together with a linker script that treats .sframe differently than the
default linker script.
https://sourceware.org/pipermail/binutils/2026-January/147826.html

Further, with SFrame sections to be soon marked KEEP for fixing
GC/SFrame (PR ld/32769), the presence of these linker generated SFrame
sections will also cause emission of an empty .sframe (for x86_64 and
s390x), even when all input bfd's have no .sframe section.

This patch avoids creation of .sframe for .plt* if none of the input
BFDs had any .sframe section.  This then avoids creation of empty
.sframe in linked objects on x86_64 and s390x, when none of the inputs
have SFrame sections.  This also fixes PR ld/33830.

For the code changes:
Reviewed-by: Jens Remus <jremus@linux.ibm.com>

New testcases have (since the above Reviewed-by) been added.  Since
--no-ld-generated-unwind-info is not supported on aarch64, add
target-specific ld tests.  Additionally add a generic test (for all
targets that support SFrame) to ensure no output .sframe is generated if
users says no --gsframe or similar.

bfd/
	PR ld/33830
	* elf-bfd.h (_bfd_elf_sframe_present_input_bfds): New
	declaration.
	* elf-sframe.c (_bfd_elf_sframe_present_input_bfds): New
	definition.
	* elf64-s390.c (elf_s390_create_dynamic_sections): Do not
	generate .sframe for .plt unconditionally.
	* elfxx-x86.c (_bfd_x86_elf_link_setup_gnu_properties):
	Likewise.
ld/testsuite/
	PR ld/33830
	* ld-s390/no-sframe.ld: Linker script with no specification for
	SFrame sections.
	* ld-s390/s390.exp: Add new test.
	* ld-s390/sframe-command-line-2.d: New testcase that uses
	--no-ld-generated-unwind-info and a linker script that has no
	specific rules for .sframe.
	* ld-x86-64/no-sframe.ld: Likewise for x86_64.
	* ld-x86-64/sframe-command-line-2.d: Likewise for x86_64.
	* ld-x86-64/x86-64.exp: Add new test.
	* ld-sframe/no-ld-generated-sframe.d: Ensure no .sframe in
	output if no .sframe in input.
	* ld-sframe/no-sframe.ld: Linker script with no specification
	for SFrame sections.
	* ld-sframe/test.s: Add new test.