The problem comes from -L="/mnt/c/Users/camin/Documents/opt/riscv/lib/gcc/riscv64-unknown-elf/10.2.0/libgcc.a" you must only give the path to the L option. Your option should be :-L="/mnt/c/Users/camin/Documents/opt/riscv/lib/gcc/riscv64-unknown-elf/10.2.0"
the enable-multilib is working well, it only provide libraries for set of archs. However be careful to give the path of the libgcc corresponding to your arch. When you enable multilib the default one will be a 64 bit versions. Normally for rv32i, the option you need is :-L="/mnt/c/Users/camin/Documents/opt/riscv/lib/gcc/riscv64-unknown-elf/10.2.0/rv32i/ilp32".
If you don’t give the good library you will probably get ABI is incompatible with that of the selected emulation error.
It would be easier to use the riscv64-unknown-elf-gcc driver to make the link because he knows all the options better. Normally it will find the necessary libraries (libgcc, libgloss ….) automatically for your arch.
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