Using Multi-Config for Multilibs

build.sh

$ cmake -G "Ninja Multi-Config" -DCMAKE_TOOLCHAIN_FILE=${HOME}/fuchsia/scripts/clang/ToolChain.cmake -C ../Cache.cmake -DCMAKE_CONFIGURATION_TYPES=rv32i\;rv32iac\;rv32im\;rv32imafc -DCMAKE_CROSS_CONFIGS=all -DCMAKE_DEFAULT_CONFIGS=all ..

Cache.cmake

set(CMAKE_C_COMPILER_TARGET "riscv32-unknown-elf" CACHE STRING "")
set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY CACHE STRING "")

set(CMAKE_C_FLAGS "--target=riscv32-unknown-elf" CACHE STRING "")
set(CMAKE_C_FLAGS_RV32I "-march=rv32i -mabi=ilp32" CACHE STRING "")
set(CMAKE_C_FLAGS_RV32IAC "-march=rv32iac -mabi=ilp32" CACHE STRING "")
set(CMAKE_C_FLAGS_RV32IM "-march=rv32im -mabi=ilp32" CACHE STRING "")
set(CMAKE_C_FLAGS_RV32IMAFC "-march=rv32imafc -mabi=ilp32f" CACHE STRING "")

set(OUTPUT_DIRECTORIES
  $<$<CONFIG:rv32i>:${CMAKE_BINARY_DIR}/lib/rv32i/ilp32>
  $<$<CONFIG:rv32iac>:${CMAKE_BINARY_DIR}/lib/rv32iac/ilp32>
  $<$<CONFIG:rv32im>:${CMAKE_BINARY_DIR}/lib/rv32im/ilp32>
  $<$<CONFIG:rv32imafc>:${CMAKE_BINARY_DIR}/lib/rv32imafc/ilp32f>
)
string(REPLACE ";" "" OUTPUT_DIRECTORIES "${OUTPUT_DIRECTORIES}")

set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${OUTPUT_DIRECTORIES}" CACHE STRING "")

CMakeLists.txt

cmake_minimum_required(VERSION 3.16)
project(Foo C)

add_library(foo STATIC foo.c)

foo.c

int foo() {
  return 0;
}