From 07c1b41bc0d960b6e2509332f96f72439fe88864 Mon Sep 17 00:00:00 2001
From: Simon Marlow <marlowsd@gmail.com>
Date: Fri, 13 Nov 2009 12:57:19 +0000
Subject: [PATCH] Tweak to the directory-building rule So we don't try to
 recreate directories just because they are older than
 mkdirhier, since mkdirhier won't touch them.

---
 ghc.mk |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/ghc.mk b/ghc.mk
index 755b9ae..26dc314 100644
--- a/ghc.mk
+++ b/ghc.mk
@@ -411,7 +411,11 @@ endif
 # Don't try to delete directories:
 .PRECIOUS: %/.
 
-%/. : $(MKDIRHIER)
+# Create build directories on demand.  NB. the | below: this indicates
+# that $(MKDIRHIER) is an order-only dependency, which means that this
+# rule fires after building mkdirhier, but we won't try to recreate
+# directories if mkdirhier changes.
+%/. : | $(MKDIRHIER)
 	"$(MKDIRHIER)" $@
 
 # -----------------------------------------------------------------------------
-- 
1.7.10.4