Add a "make-command" utility Makefile function

ghc.mk

@@ -146,6 +146,11 @@ $(error $$(GhcLibWays) is empty, it must contain at least one way)
 endif
 endif
 
+# -----------------------------------------------------------------------------
+# Utility definitions
+
+include rules/make-command.mk
+
 # -----------------------------------------------------------------------------
 # Macros for standard targets
 

rules/make-command.mk

+# -----------------------------------------------------------------------------
+#
+# (c) 2010 The University of Glasgow
+#
+# This file is part of the GHC build system.
+#
+# To understand how the build system works and how to modify it, see
+#      http://hackage.haskell.org/trac/ghc/wiki/Building/Architecture
+#      http://hackage.haskell.org/trac/ghc/wiki/Building/Modifying
+#
+# -----------------------------------------------------------------------------
+
+# $1 = the line
+# The formatting of this definition (in particular, the blank line at
+# the start) is important, in order to get make to generate the right
+# makefile code.
+
+define make-command
+
+	$1
+endef