fix(tests): improve check to assert echo exists in path

Author: veera-sivarajan

tests/run-make-fulldeps/hotplug_codegen_backend/Makefile

@@ -6,8 +6,11 @@ include ../../run-make/tools.mk
 # backends and that this external codegen backend is only included in the dep info if
 # -Zbinary-dep-depinfo is used.
 
+REQUIRED := echo # This test requires `echo` to exist
+$(foreach bin,$(REQUIRED),\
+    $(if $(shell command -v $(bin) 2> /dev/null),,$(error Error: Please install `$(bin)`)))
+
 all:
-	/bin/echo || exit 0 # This test requires /bin/echo to exist
 	$(RUSTC) the_backend.rs --crate-name the_backend --crate-type dylib \
 		-o $(TMPDIR)/the_backend.dylib