How do I upload an Arduino STM32 binary from the Mac command line?
There are several different tools for uploading binaries to a Cortex M3.  Depending on the board (not chip) configuration, they include (ht: Majenko):


dfu-util through an FT232 adapter
stm32flash through serial
micronucleus through the Micronucleus bootloader
stlink through an STLink programmer


Many Arduino flavors use a board with some kind of USB or FT232 adapter.  In this case:

the STM32 line of processors include a DFU (device firmware update) bootloader in ROM.

The dfu-util project supports a Mac version of dfu-util, their command line DFU tool.

Note that this answer is identical for any binaries which run on the processor, be they Arduino sketches or programs developed with other frameworks.