george@nomad ~/tmp/chad/nim/blinky ±master » nimble build --verbose --os:standalone
    Setting Nim stdlib prefix to
    Setting Nim stdlib path to /home/george/.choosenim/toolchains/nim-0.18.0/lib
  Verifying dependencies for blinky@0.1.0
   Building blinky/blinky using c backend
     Error: Build failed for package: blinky
        ... Details:
        ... Execution failed with exit code 1
        ... Command: "/home/george/.nimble/bin/nim" c --noBabelPath --os:standalone -o:"/home/george/tmp/chad/nim/blinky/bin/blinky" "/home/george/tmp/chad/nim/blinky/src/blinky.nim"
        ... Output: Hint: used config file '/home/george/.choosenim/toolchains/nim-0.18.0/config/nim.cfg' [Conf]
        ... Hint: used config file '/home/george/tmp/chad/nim/blinky/src/blinky.nim.cfg' [Conf]
        ... Hint: system [Processing]
        ... Hint: blinky [Processing]
        ... blinky.nim(1, 6) Hint: 'blinky.main()[declared in blinky.nim(1, 5)]' is declared but not used [XDeclaredButNotUsed]
        ... Hint:  [Link]
        ... /usr/lib/gcc/arm-none-eabi/5.4.1/../../../arm-none-eabi/lib/libc.a(lib_a-exit.o): In function `exit':
        ... /build/newlib-OTNHfJ/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/stdlib/../../../../../newlib/libc/stdlib/exit.c:70: undefined reference to `_exit'
        ... collect2: error: ld returned 1 exit status
        ... Error: execution of an external program failed: '/usr/bin/arm-none-eabi-gcc   -o /home/george/tmp/chad/nim/blinky/bin/blinky  /home/george/tmp/chad/nim/blinky/src/nimcache/blinky_blinky.o /home/george/tmp/chad/nim/blinky/src/nimcache/stdlib_system.o    '