builder/cmake: Fix native linker failure by providing compiler flags to linker
builder/cmake: Fix native linker failure by providing compiler flags to linker

Generated cmake scripts are missing `-m32` architecture linker flag
which leads to following linker error on native:

  ld: i386 architecture of input file `blinky/null.c.obj' is incompatible with i386:x86-64 output

I've fixed it by providing compiler flags to the linker as it seems to
be used by `newt build` command.

This is CMake linker command:

  gcc -lm -lutil -o libblinky.elf
   -Wl,--start-group
       <snipped>
   -Wl,--end-group

This is linker command as generated by `newt build` command:

  gcc -o blinky.elf
   -DAPP_NAME=blinky -DAPP_blinky -DARCH_NAME=sim -DARCH_sim
   -DBSP_NAME=native -DBSP_native -DMN_LINUX -DMYNEWT=1 -O0 -Wall -Werror
   -Wno-unused-result -ggdb -m32
   -Wl,--start-group
       <snipped>
   -Wl,--end-group -lm -lutil

Signed-off-by: Petr Štetiar <f0d4d86d9c7002e67e6ae7bb5596bc0afa7b4c3a@true.cz>

apache/incubator-mynewt-newt,apache/incubator-mynewt-newt