I managed to compile and flash bluepill-systick and the led blinks as expected. However, when I try to debug in vscode, the breakpoints that I set in main.cpp get disabled (become open circles) and do not fire. Hovering mouse over the breakpoint shows "No source file named /****/src/main.cpp.", although this file exists. Strangely, I can set breakpoints and step in libopencm3 code, but not in main.cpp. Maybe this is an issue where relative and absolute paths get confused somehow?