Merge pull request #2183 from Pinata-Consulting/makefile-fewer-klayout-invocations

makefile: reduce number of shell invocations

Author: maliberty

flow/Makefile

@@ -301,7 +301,9 @@ KLAYOUT_BIN_FROM_DIR = $(KLAYOUT_DIR)/klayout
 ifeq ($(wildcard $(KLAYOUT_BIN_FROM_DIR)), $(KLAYOUT_BIN_FROM_DIR))
 KLAYOUT_CMD ?= sh -c 'LD_LIBRARY_PATH=$(dir $(KLAYOUT_BIN_FROM_DIR)) $$0 "$$@"' $(KLAYOUT_BIN_FROM_DIR)
 else
-KLAYOUT_CMD ?= $(shell command -v klayout)
+ifeq ($(KLAYOUT_CMD),)
+KLAYOUT_CMD := $(shell command -v klayout)
+endif
 endif
 KLAYOUT_FOUND            = $(if $(KLAYOUT_CMD),,$(error KLayout not found in PATH))
 
@@ -393,7 +395,7 @@ do-klayout_tech:
 	cp $(TECH_LEF) $(OBJECTS_DIR)/klayout_tech.lef
 
 KLAYOUT_ENV_VAR_IN_PATH_VERSION = 0.28.11
-KLAYOUT_VERSION = $(shell $(KLAYOUT_CMD) -v 2>/dev/null | grep 'KLayout' | cut -d ' ' -f2)
+KLAYOUT_VERSION := $(shell $(KLAYOUT_CMD) -v 2>/dev/null | grep 'KLayout' | cut -d ' ' -f2)
 
 KLAYOUT_ENV_VAR_IN_PATH = $(shell \
 	if [ -z "$(KLAYOUT_VERSION)" ]; then \