Update Makefile

work around pdk version check for openlane

Makefile

diff --git a/Makefile b/Makefile
index 71e0b8c..ee141aa 100644
--- a/Makefile
+++ b/Makefile
@@ -24,6 +24,7 @@
 export OPEN_PDKS_COMMIT?=7519dfb04400f224f140749cda44ee7de6f5e095
 export PDK_MAGIC_COMMIT=7d601628e4e05fd17fcb80c3552dacb64e9f6e7b
 export OPENLANE_TAG=2022.04.08_02.45.18
+export MISMATCHES_OK=1
 
 # Install lite version of caravel, (1): caravel-lite, (0): caravel
 CARAVEL_LITE?=1