Update Makefile

### Description
- Setting the python to explicitly to python3

Author: ruck314

Makefile

@@ -34,7 +34,7 @@ GHDLFLAGS = --workdir=$(OUT_DIR) --ieee=synopsys -fexplicit -frelaxed-rules  --w
 include $(RUCKUS_DIR)/system_shared.mk
 
 # Override system_shared.mk build string
-export BUILD_SVR_TYPE = $(shell python -m platform)
+export BUILD_SVR_TYPE = $(shell python3 -m platform)
 export GHDL_VERSION   = $(shell ghdl -v 2>&1 | head -n 1)
 export BUILD_STRING   = $(PROJECT): $(GHDL_VERSION), $(BUILD_SYS_NAME) ($(BUILD_SVR_TYPE)), Built $(BUILD_DATE) by $(BUILD_USER)