[ci] fix actions job

disable default printf

Author: stnolting

.github/workflows/vunit.yml

@@ -27,6 +27,7 @@ jobs:
           make -C neorv32/sw/example/processor_check
           clean_all
           USER_FLAGS+=-DUART0_SIM_MODE
+          USER_FLAGS+=-DSUPPRESS_OPTIONAL_UART_PRINT
           USER_FLAGS+=-flto
           MARCH=rv32imac_zicsr_zifencei
           RISCV_PREFIX=riscv32-unknown-elf-