Update Makefile

Makefile

diff --git a/Makefile b/Makefile
index c9c8594..70d6251 100644
--- a/Makefile
+++ b/Makefile
@@ -25,13 +25,13 @@
 export PDK_MAGIC_COMMIT=7d601628e4e05fd17fcb80c3552dacb64e9f6e7b
 export OPENLANE_TAG=2022.02.23_02.50.41
 export MISMATCHES_OK=1
-export PDKPATH?=$(PDK_ROOT)/sky130B
 
 # Install lite version of caravel, (1): caravel-lite, (0): caravel
 CARAVEL_LITE?=1
 
 # PDK switch varient
 export PDK?=sky130B
+export PDKPATH?=$(PDK_ROOT)/$(PDK)
 
 MPW_TAG ?= mpw-6c