Update Makefile PDK_PATH

verilog/dv/la_test1/Makefile

diff --git a/verilog/dv/la_test1/Makefile b/verilog/dv/la_test1/Makefile
index b23075d..14d6ee6 100644
--- a/verilog/dv/la_test1/Makefile
+++ b/verilog/dv/la_test1/Makefile
@@ -14,6 +14,9 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+## PDK 
+PDK_PATH = $(PDK_ROOT)/sky130A
+
 ## Caravel Pointers
 CARAVEL_ROOT ?= ../../../caravel
 CARAVEL_PATH ?= $(CARAVEL_ROOT)
@@ -59,7 +62,7 @@
 %.vcd: %.vvp
 	vvp $<
 
-%.elf: %.c $(CARAVEL_FIRMWARE_PATH)/sections.lds $(CARAVEL_FIRMWARE_PATH)/start.s
+%.elf: %.c $(CARAVEL_FIRMWARE_PATH)/sections.lds $(CARAVEL_FIRMWARE_PATH)/start.s check-env
 	${GCC_PATH}/${GCC_PREFIX}-gcc -I $(CARAVEL_PATH) -march=rv32imc -mabi=ilp32 -Wl,-Bstatic,-T,$(CARAVEL_FIRMWARE_PATH)/sections.lds,--strip-debug -ffreestanding -nostdlib -o $@ $(CARAVEL_FIRMWARE_PATH)/start.s $<
 
 %.hex: %.elf
@@ -70,6 +73,17 @@
 %.bin: %.elf
 	${GCC_PATH}/${GCC_PREFIX}-objcopy -O binary $< /dev/stdout | tail -c +1048577 > $@
 
+check-env:
+ifndef PDK_ROOT
+	$(error PDK_ROOT is undefined, please export it before running make)
+endif
+ifeq (,$(wildcard $(PDK_ROOT)/sky130A))
+	$(error $(PDK_ROOT)/sky130A not found, please install pdk before running make)
+endif
+ifeq (,$(wildcard $(GCC_PATH)/$(GCC_PREFIX)-gcc ))
+	$(error $(GCC_PATH)/$(GCC_PREFIX)-gcc is not found, please export GCC_PATH and GCC_PREFIX before running make)
+endif
+
 # ---- Clean ----
 
 clean: