cmake: Add esp32c3 toolchain file

tools/cmake/toolchain-esp32c3.cmake

@@ -0,0 +1,9 @@
+set(CMAKE_SYSTEM_NAME Generic)
+
+set(CMAKE_C_COMPILER riscv32-esp-elf-gcc)
+set(CMAKE_CXX_COMPILER riscv32-esp-elf-g++)
+set(CMAKE_ASM_COMPILER riscv32-esp-elf-gcc)
+
+set(CMAKE_C_FLAGS "-march=rv32imc" CACHE STRING "C Compiler Base Flags")
+set(CMAKE_CXX_FLAGS "-march=rv32imc" CACHE STRING "C++ Compiler Base Flags")
+set(CMAKE_EXE_LINKER_FLAGS "-nostartfiles -march=rv32imc --specs=nosys.specs" CACHE STRING "Linker Base Flags")