CI: build all platforms in the same stage

Signed-off-by: Adam Wujek <dev_public@wujek.eu>
5 jobs from adam-dev in 1 minute and 26 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build Fw
passed #9997
arm-clang-coast
make_bootloader_fw

00:13

passed #9995
arm-clang-coast
make_main_fw_fant

00:19

passed #9996
arm-clang-coast
make_main_fw_rato

00:16

passed #9994
arm-clang-coast
make_main_fw_rtsb

00:17

passed #9998
arm-clang-coast
make_test_master_fw

00:18