Comment # 2 on bug 1171405 from Matwey Kornilov

You are right, the issue is present when dummy C file is compiled as the
following:

# avr-gcc -v -mmcu=atmega1284p test.c

Using built-in specs.
Reading specs from /usr/lib64/gcc/avr/10/device-specs/specs-atmega1284p
COLLECT_GCC=avr-gcc
COLLECT_LTO_WRAPPER=/usr/lib64/gcc/avr/10/lto-wrapper
Target: avr
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
--enable-languages=c,c++ --enable-checking=release --disable-werror
--with-gxx-include-dir=/usr/include/c++/10 --enable-ssp --disable-libssp
--disable-libvtv --disable-cet --disable-libcc1 --disable-plugin
--with-bugurl=https://bugs.opensuse.org/ --with-pkgversion='SUSE Linux'
--with-slibdir=/lib64 --with-system-zlib --enable-libstdcxx-allocator=new
--disable-libstdcxx-pch --enable-version-specific-runtime-libs
--with-gcc-major-version-only --enable-linker-build-id --enable-linux-futex
--enable-gnu-indirect-function --program-suffix=-10 --program-prefix=avr-
--target=avr --disable-nls --with-sysroot=/usr/avr/sys-root
--with-build-sysroot=/usr/avr/sys-root --with-build-time-tools=/usr/avr/bin
--enable-lto --without-gxx-include-dir --with-native-system-header-dir=/include
--build=x86_64-suse-linux --host=x86_64-suse-linux
Thread model: single
Supported LTO compression algorithms: zlib
gcc version 10.1.1 20200507 [revision dd38686d9c810cecbaa80bb82ed91caaa58ad635]
(SUSE Linux) 
COLLECT_GCC_OPTIONS='-v'  '-mdouble=32' '-mlong-double=64'
'-specs=device-specs/specs-atmega1284p' '-mmcu=avr51'
 /usr/lib64/gcc/avr/10/cc1 -quiet -v -imultilib avr51 -D__AVR_ATmega1284P__
-D__AVR_DEVICE_NAME__=atmega1284p test.c -mn-flash=2 -mno-skip-bug -quiet
-dumpbase test.c -mdouble=32 -mlong-double=64 -mmcu=avr51 -auxbase test
-version -o /tmp/ccLCyfEk.s
GNU C17 (SUSE Linux) version 10.1.1 20200507 [revision
dd38686d9c810cecbaa80bb82ed91caaa58ad635] (avr)
        compiled by GNU C version 7.5.0, GMP version 6.1.2, MPFR version 4.0.1,
MPC version 1.1.0, isl version isl-0.18-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/avr/sys-root/usr/local/include"
ignoring nonexistent directory "/usr/lib64/gcc/avr/10/../../../../avr/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib64/gcc/avr/10/include
 /usr/lib64/gcc/avr/10/include-fixed
 /usr/avr/sys-root/include
End of search list.
GNU C17 (SUSE Linux) version 10.1.1 20200507 [revision
dd38686d9c810cecbaa80bb82ed91caaa58ad635] (avr)
        compiled by GNU C version 7.5.0, GMP version 6.1.2, MPFR version 4.0.1,
MPC version 1.1.0, isl version isl-0.18-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 00000000000000000000000000000000
COLLECT_GCC_OPTIONS='-v'  '-mdouble=32' '-mlong-double=64'
'-specs=device-specs/specs-atmega1284p' '-mmcu=avr51'
 /usr/lib64/gcc/avr/10/as -mmcu=avr51 -mgcc-isr -mno-skip-bug -o
/tmp/cc6EkzVk.o /tmp/ccLCyfEk.s
COMPILER_PATH=/usr/lib64/gcc/avr/10/:/usr/lib64/gcc/avr/10/:/usr/lib64/gcc/avr/:/usr/lib64/gcc/avr/10/:/usr/lib64/gcc/avr/:/usr/lib64/gcc/avr/10/../../../../avr/bin/
LIBRARY_PATH=/usr/lib64/gcc/avr/10/avr51/:/usr/avr/sys-root/lib/avr51/:/usr/lib64/gcc/avr/10/:/usr/lib64/gcc/avr/10/../../../../avr/lib/:/usr/avr/sys-root/lib/
COLLECT_GCC_OPTIONS='-v'  '-mdouble=32' '-mlong-double=64'
'-specs=device-specs/specs-atmega1284p' '-mmcu=avr51'
 /usr/lib64/gcc/avr/10/collect2 -plugin /usr/lib64/gcc/avr/10/liblto_plugin.so
-plugin-opt=/usr/lib64/gcc/avr/10/lto-wrapper
-plugin-opt=-fresolution=/tmp/cchQFPdl.res -plugin-opt=-pass-through=-lgcc
-plugin-opt=-pass-through=-lm -plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-latmega1284p --sysroot=/usr/avr/sys-root --build-id
-mavr51 -Tdata 0x800100 /usr/avr/sys-root/lib/avr51/crtatmega1284p.o
-L/usr/lib64/gcc/avr/10/avr51 -L/usr/avr/sys-root/lib/avr51
-L/usr/lib64/gcc/avr/10 -L/usr/lib64/gcc/avr/10/../../../../avr/lib
-L/usr/avr/sys-root/lib /tmp/cc6EkzVk.o --start-group -lgcc -lm -lc
-latmega1284p --end-group
/usr/lib64/gcc/avr/10/ld: warning: -z relro ignored
/usr/lib64/gcc/avr/10/ld: skipping incompatible
/usr/lib64/gcc/avr/10/avr51/libgcc.a when searching for -lgcc
/usr/lib64/gcc/avr/10/ld: skipping incompatible /usr/lib64/gcc/avr/10/libgcc.a
when searching for -lgcc
/usr/lib64/gcc/avr/10/ld: cannot find -lgcc
collect2: error: ld returned 1 exit status