Here is an issue that one of my students encountered today: https://stackoverflow.com/questions/70069809/unrecognized-emulation-mode-ain-when-compiling-with-gcc-on-ubuntu/70069810

Consider any simple C++ program in a file named `main.cpp`. I compile it with `g++ main.cpp -o main`, but I accidentally add a dash before `main`:

g++ main.cpp -o -main

Expected behavior: the program is compiled to a file named `-main`.

Real behavior:
/usr/bin/ld: unrecognised emulation mode: ain
Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu elf_l1om elf_k1om i386pep i386pe
collect2: error: ld returned 1 exit status

My understanding: GCC treats `-main` as both `-m` option (targeting some unexisting `ain` architecture) AND name for the output file.

For example, on my 64-bit Ubuntu I can write

g++ main.cpp -o -melf_x86_64

and it will produce a binary named `-melf_x86_64`. However, the following command fails because I don't have 32-bit standard library installed:

g++ main.cpp -o -melf_i386

yields:

/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/9/libstdc++.so when searching for -lstdc++
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/9/libstdc++.a when searching for -lstdc++
/usr/bin/ld: cannot find -lstdc++
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libm.so when searching for -lm
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libm.a when searching for -lm
/usr/bin/ld: skipping incompatible /lib/x86_64-linux-gnu/libm.so when searching for -lm
/usr/bin/ld: skipping incompatible /lib/x86_64-linux-gnu/libm.a when searching for -lm
/usr/bin/ld: skipping incompatible /usr/lib/x86_64-linux-gnu/libm.so when searching for -lm
/usr/bin/ld: skipping incompatible /usr/lib/x86_64-linux-gnu/libm.a when searching for -lm
/usr/bin/ld: skipping incompatible /usr/lib/x86_64-linux-gnu/libm.so when searching for -lm
/usr/bin/ld: skipping incompatible /usr/lib/x86_64-linux-gnu/libm.a when searching for -lm
/usr/bin/ld: cannot find -lm
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /lib/x86_64-linux-gnu/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/lib/x86_64-linux-gnu/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/9/libgcc.a when searching for -lgcc
/usr/bin/ld: cannot find -lgcc
collect2: error: ld returned 1 exit status

I suspect some other options may be be affected as well. `-m` here is special only because `main` start with `m`.

Being able to read the option in two different ways simultaneously looks like a bug in my world.

I can reproduce the behavior on a wide range of OSes: msys2 on Windows 10 (g++ 11.2.0), g++ 9.3.0 on 64-bit Ubuntu 20.04.3 LTS, as well as trunk version on Godbolt.