From 7d3bc2cfba0f65306cd323a4e17204e260190183 Mon Sep 17 00:00:00 2001
From: Olaf Seibert <rhialto@falu.nl>
Date: Fri, 12 Feb 2016 20:32:14 +0100
Subject: [PATCH] Add carefully crafted Makefile for recursing into
 subdirectories...

that is compatile with both real Make and GNU Make.
---
 configure.ac |  1 +
 mk/bld.mk    | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 mk/bld.mk

diff --git a/configure.ac b/configure.ac
index 91a41f9..91b9a7e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -246,6 +246,7 @@ AC_SUBST([CENVFLAGS])
 AC_CONFIG_FILES([bld-kl/Makefile:mk/top.mk:mk/top-kl.mk:src/Makefile.mk
                  bld-ks/Makefile:mk/top.mk:mk/top-ks.mk:src/Makefile.mk
                  bld-ks-its/Makefile:mk/top.mk:mk/top-ks-its.mk:src/Makefile.mk
+		 Makefile:mk/bld.mk
 		])
 
 AC_OUTPUT
diff --git a/mk/bld.mk b/mk/bld.mk
new file mode 100644
index 0000000..936689a
--- /dev/null
+++ b/mk/bld.mk
@@ -0,0 +1,28 @@
+# Makefile to build in the subdirectories.
+# Designed to be both BSD Make and GNU Make compatible
+# (as are all the other Makefiles).
+#
+
+# The RECURSE macro uses a shell variable $TARGET for delayed expansion.
+RECURSE=for d in bld-* ; \
+	do \
+	    ${MAKE} -C $$d $${TARGET} ; \
+	done
+
+# This carefully crafted rule will run Make in all subdirectories with
+# the same target, no matter what it is (as long as it is just one
+# target).
+#
+# .TARGETS is a BSD specific variable, and MAKECMDGOALS is the GNU version.
+# .TARGETS becomes "rEmOvEmE" when no targets are given on the
+# command line (because this is the default target).
+# MAKECMDGOALS remains empty in that case.
+# Do not use "all" as the extra target, since that fails when that is
+# given as target on the command line (you get duplicate targets).
+# The shell variable substitution removes "rEmOvEmE" if present.
+# So when no target is given, the recursion uses no target either.
+
+${.TARGETS} ${MAKECMDGOALS} rEmOvEmE :
+#	set -x; T="${.TARGETS}${MAKECMDGOALS}"; echo "T=$$T"; TARGET="$${T%%rEmOvEmE}"; echo "TARGET=$$TARGET"
+	T="${.TARGETS}${MAKECMDGOALS}"; TARGET="$${T%%rEmOvEmE}"; ${RECURSE}
+