libc/arm: add missing .cfi_sections

libc/arm: add missing .cfi_sections

The modifications added by the series "M-profile PACBTI-enablement"
(see 9d6b00511e50a54d2472d11f75f7c0f2b4a98b24) have introduced a couple
of .cfi_* instructions.

Like for e6459123e497409a9e3d845c39829a9602ba55a4, these instructions
create object files which contain .eh_frame sections.  However, ARM uses
its own unwind info format, not .eh_frame, which is generated by
ARM-specific directives, not .cfi_*. The .eh_frame sections are useless,
but also not removed by strip and may be harmful with some linker
scripts.

Adding ".cfi_sections .debug_frame" (as in glibc) moves the generated
directives towards .debug_frame instead of .eh_frame. Making them easier
to handle.

            * libc/machine/arm/aeabi_memmove-thumb2.S: Use .cfi_sections
            .debug_frame.
            * libc/machine/arm/aeabi_memset-thumb2.S: Likewise.
            * libc/machine/arm/memchr.S: Likewise.
            * libc/machine/arm/memcpy-armv7m.S: Likewise.
            * libc/machine/arm/setjmp.S: Likewise.
            * libc/machine/arm/strlen-armv7.S: Likewise.
            * libc/machine/arm/strlen-thumb2-Os.S: Likewise.