Change non-portable echo -n to printf.
--- mk/elftoolchain.tex.mk.orig	2012-08-27 22:39:09.000000000 -0500
+++ mk/elftoolchain.tex.mk	2021-07-02 10:41:45.000000000 -0500
@@ -88,7 +88,7 @@
 .else
 
 all clean clobber depend install obj:	.PHONY .SILENT
-	echo -n WARNING: make \"${.TARGET}\" in \"${.CURDIR:T}\" skipped:
+	printf "WARNING: make \"%s\" in \"%s\" skipped:" "${.TARGET}" "${.CURDIR:T}"
 .if	defined(MKTEX) && ${MKTEX} == "yes"
 	echo " missing tools."
 .else
