Makefile change to support newer arm compilers

[prismv]

Please change the Makefile according to the proposed patch of @LdBeth in #1427, because it allows the usage of current versions of arm cross-compilers :

-specs=nano.specs -specs=nosys.specs added to PLATFORM_FLAGS and LINK_OPTS.

An alternative proposal might be to allow external definitions by setting these variables only with += within Makefile to allow addition of such setting on make call.

Compilation works then e.g. with:

❯ arm-none-eabi-c++ --version
arm-none-eabi-c++ (Arch Repository) 14.2.0
Copyright (C) 2024 Free Software Foundation, Inc.

[prismv]

Checked elf size information (and pgm size explicitely, too) of 3 variants based on 0.9.2 code:

unmodified code, arm-none-eabi-g++ (GNU Arm Embedded Toolchain 10.3-2021.10) 10.3.1 20210824 (release)

❯ arm-none-eabi-size -A build/dm42/release/db48x.elf
build/dm42/release/db48x.elf  :
section             size         addr
.qspi             279296   2415919104
.rodata            84280    134545408
.text             568320    134629696
.ARM.extab             0    135198016
.ARM                   8    135198016
.preinit_array         0    135198024
.init_array           24    135198024
.fini_array            8    135198048
.data               4584    268435456
.bss                3432    268440040
.ARM.attributes       48            0
.comment              73            0
.debug_frame        7756            0
Total             947829

pgm file size is 657252.

Makefile with nano and nosys specs, arm-none-eabi-g++ (GNU Arm Embedded Toolchain 10.3-2021.10) 10.3.1 20210824 (release)

❯ arm-none-eabi-size -A build/dm42/release/db48x.elf
build/dm42/release/db48x.elf  :
section             size         addr
.qspi             279296   2415919104
.rodata            83872    134545408
.text             542160    134629280
.ARM.extab             0    135171440
.ARM                   8    135171440
.preinit_array         0    135171448
.init_array           16    135171448
.fini_array            8    135171464
.data               3608    268435456
.bss                3424    268439064
.ARM.attributes       48            0
.comment              73            0
.debug_frame        6056            0
Total             918569

pgm file size is 629692 bytes.

Makefile with nano and nosys specs, arm-none-eabi-g++ (Arch Repository) 14.2.0

❯ arm-none-eabi-size -A build/dm42/release/db48x.elf
build/dm42/release/db48x.elf  :
section              size         addr
.qspi              279280   2415919104
.rodata             83688    134545408
.text              547848    134629104
.ARM.extab              0    135176952
.ARM                    8    135176952
.preinit_array          0    135176960
.init_array            16    135176960
.fini_array             8    135176976
.data                3592    268435456
.bss                 4136    268439048
.ARM.attributes        48            0
.comment               30            0
.debug_line         49788            0
.debug_line_str       378            0
.debug_info        117942            0
.debug_abbrev       28855            0
.debug_aranges       3248            0
.debug_str          12867            0
.debug_frame         6156            0
.debug_loclists     33638            0
.debug_rnglists      2464            0
Total             1173990

pgm file size is 635188 bytes.

[prismv]

Pull request: #1431