Just in time compilation for riscv32 architecture

[pguyot]

Continuation of:

• Cross compile armhf and s390x builds #1881
• Just in time compilation with armv6m target #1829
• JIT: add float32 variant for single precision floats #1891
• JIT: optimize op_return by not always returning to VM #1838
• JIT: optimize shift right for platforms with 3 operands #1900
• JIT: factorize tail calls to reduce binary size #1901
• JIT (armv6m): use literal pool to reduce binary size #1903
• Fix several CMake dependencies and remove armv4t cross build #1981

Initial implementation of riscv32 assembler and backend. Tested on unix with qemu-user and on esp32c3.

	native (w42/jit-riscv) -- 2a93583	emulated (main) -- f8bdc7d	%
pingpong_speed_test	13494702	51717135	74 %
prime_speed_test	9976144	28151722	65 %
prng_test	1246860	1993737	37 %
pi_test	27677061	35485204	22 %
sudoku_solution_test	4297754	5672230	24 %
sudoku_puzzle_test	176939584	277931484	36 %

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

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