versions.txt: non-zero exit code when commands don't exist

use-case: in bazel-orfs when generating issues for floorplan, yosys isn't a
dependency and hence isn't in e.g. the
`bazelisk build MockArray_floorplan --sandbox_debug` environment.

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/Makefile

@@ -184,17 +184,9 @@ $(foreach block,$(BLOCKS),$(eval $(WORK_HOME)/results/$(PLATFORM)/$(DESIGN_NICKN
 .PHONY: versions.txt
 versions.txt:
 	mkdir -p $(OBJECTS_DIR)
-	@if [ -z "$(YOSYS_EXE)" ]; then \
-		echo >> $(OBJECTS_DIR)/$@ "yosys not installed"; \
-	else \
-		$(YOSYS_EXE) -V > $(OBJECTS_DIR)/$@; \
-	fi
-	@echo openroad `$(OPENROAD_EXE) -version` >> $(OBJECTS_DIR)/$@
-	@if [ -z "$(KLAYOUT_CMD)" ]; then \
-		echo >> $(OBJECTS_DIR)/$@ "klayout not installed"; \
-	else \
-		$(KLAYOUT_CMD) -zz -v >> $(OBJECTS_DIR)/$@; \
-	fi
+	@echo yosys $(shell $(YOSYS_EXE) -V) > $(OBJECTS_DIR)/$@
+	@echo openroad $(shell $(OPENROAD_EXE) -version) >> $(OBJECTS_DIR)/$@
+	@echo klayout $(shell $(KLAYOUT_CMD) -zz -v) >> $(OBJECTS_DIR)/$@
 
 # Pre-process libraries
 # ==============================================================================