diff -r 50ef71b6fd3d -r dea8a62cdfc3 make/autoconf/basics.m4
--- a/make/autoconf/basics.m4	Tue Oct 09 07:33:15 2018 -0400
+++ b/make/autoconf/basics.m4	Tue Oct 09 14:57:23 2018 -0700
@@ -569,7 +569,8 @@
   BASIC_REQUIRE_PROGS(GZIP, pigz gzip)
   BASIC_REQUIRE_PROGS(LN, ln)
   BASIC_REQUIRE_PROGS(LS, ls)
-  BASIC_REQUIRE_PROGS(MKDIR, mkdir)
+  # gmkdir is known to be safe for concurrent invocations with -p flag.
+  BASIC_REQUIRE_PROGS(MKDIR, [gmkdir mkdir])
   BASIC_REQUIRE_PROGS(MKTEMP, mktemp)
   BASIC_REQUIRE_PROGS(MV, mv)
   BASIC_REQUIRE_PROGS(NAWK, [nawk gawk awk])