I was able to figure it out, though it's still finnicky.
Trying to build c++ for raspberry pi pico I get this build log.

18:12:25 **** Build of configuration Debug for project Pico_Learning ****
make all 
arm-none-eabi-gcc "../rt-thread/src/clock.c"
arm-none-eabi-gcc "../rt-thread/src/components.c"
arm-none-eabi-gcc "../rt-thread/src/device.c"
arm-none-eabi-gcc "../rt-thread/src/idle.c"
arm-none-eabi-gcc "../rt-thread/src/ipc.c"
arm-none-eabi-gcc "../rt-thread/src/irq.c"
arm-none-eabi-gcc "../rt-thread/src/kservice.c"
arm-none-eabi-gcc "../rt-thread/src/mem.c"
arm-none-eabi-gcc "../rt-thread/src/mempool.c"
arm-none-eabi-gcc "../rt-thread/src/object.c"
arm-none-eabi-gcc "../rt-thread/src/scheduler.c"
arm-none-eabi-gcc "../rt-thread/src/thread.c"
arm-none-eabi-gcc "../rt-thread/src/timer.c"
arm-none-eabi-gcc "../rt-thread/libcpu/arm/cortex-m0/context_gcc.S"
arm-none-eabi-gcc "../rt-thread/libcpu/arm/cortex-m0/cpuport.c"
arm-none-eabi-gcc "../rt-thread/libcpu/arm/common/backtrace.c"
arm-none-eabi-gcc "../rt-thread/libcpu/arm/common/div0.c"
arm-none-eabi-gcc "../rt-thread/libcpu/arm/common/showmem.c"
arm-none-eabi-gcc "../rt-thread/components/libc/compilers/newlib/libc.c"
arm-none-eabi-gcc "../rt-thread/components/libc/compilers/newlib/stdio.c"
arm-none-eabi-gcc "../rt-thread/components/libc/compilers/newlib/syscalls.c"
arm-none-eabi-gcc "../rt-thread/components/libc/compilers/common/stdlib.c"
arm-none-eabi-gcc "../rt-thread/components/libc/compilers/common/time.c"
arm-none-eabi-gcc "../rt-thread/components/finsh/cmd.c"
arm-none-eabi-gcc "../rt-thread/components/finsh/msh.c"
arm-none-eabi-gcc "../rt-thread/components/finsh/shell.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/src/completion.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/src/dataqueue.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/src/pipe.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/src/ringblk_buf.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/src/ringbuffer.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/src/waitqueue.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/src/workqueue.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/serial/serial.c"
arm-none-eabi-gcc "../rt-thread/components/drivers/misc/pin.c"
arm-none-eabi-gcc "../rt-thread/components/cplusplus/crt_init.c"
arm-none-eabi-g++ "../rt-thread/components/cplusplus/cxx_Mutex.cpp"
arm-none-eabi-g++ "../rt-thread/components/cplusplus/cxx_Semaphore.cpp"
arm-none-eabi-g++ "../rt-thread/components/cplusplus/cxx_Thread.cpp"
arm-none-eabi-g++ "../rt-thread/components/cplusplus/cxx_crt.cpp"
arm-none-eabi-gcc "../libraries/pico-sdk/src/rp2_common/pico_stdlib/stdlib.c"
arm-none-eabi-gcc "../libraries/pico-sdk/src/rp2_common/pico_stdio_uart/stdio_uart.c"
In file included from C:\RT-ThreadStudio\workspace\Pico_Learning\libraries\pico-sdk\src\common\pico_binary_info\include/pico/binary_info.h:24:0,
                 from ../libraries/pico-sdk/src/rp2_common/pico_stdio_uart/stdio_uart.c:9:
C:\RT-ThreadStudio\workspace\Pico_Learning\libraries\pico-sdk\src\common\pico_binary_info\include/pico/binary_info/code.h:13:25: error: operator '!' has no right operand
make: *** [libraries/pico-sdk/src/rp2_common/pico_stdio_uart/subdir.mk:18: libraries/pico-sdk/src/rp2_common/pico_stdio_uart/stdio_uart.o] Error 1
"make all" terminated with exit code 2. Build might be incomplete.

18:12:32 Build Failed. 2 errors, 0 warnings. (took 6s.929ms)