build system: re-add mistakenly deleted script

scripts/mkmakefile

@@ -0,0 +1,36 @@
+#!/bin/sh
+# Generates a small Makefile used in the root of the output
+# directory, to allow make to be started from there.
+# The Makefile also allow for more convinient build of external modules
+
+# Usage
+# $1 - Kernel src directory
+# $2 - Output directory
+# $3 - version
+# $4 - patchlevel
+
+
+test ! -r $2/Makefile -o -O $2/Makefile || exit 0
+echo "  GEN     $2/Makefile"
+
+cat << EOF > $2/Makefile
+# Automatically generated by $0: don't edit
+
+VERSION = $3
+PATCHLEVEL = $4
+
+KERNELSRC    := $1
+KERNELOUTPUT := $2
+
+MAKEFLAGS += --no-print-directory
+
+.PHONY: all \$(MAKECMDGOALS)
+
+all:
+	\$(MAKE) -C \$(KERNELSRC) O=\$(KERNELOUTPUT)
+
+Makefile:;
+
+\$(filter-out all Makefile,\$(MAKECMDGOALS)) %/:
+	\$(MAKE) -C \$(KERNELSRC) O=\$(KERNELOUTPUT) \$@
+EOF