From b39f193c31e057fd3d3d33e1813934a96d0b8e38 Mon Sep 17 00:00:00 2001
From: f0rt <f0rt@212acab6-be3b-0410-9dea-997c60f758d6>
Date: Mon, 2 May 2011 19:32:12 +0000
Subject: [PATCH] Avoid a clash when scons is run in parallel operation
 (#3295528)

git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@6151 212acab6-be3b-0410-9dea-997c60f758d6
---
 SCons/utils.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/SCons/utils.py b/SCons/utils.py
index c6562597..04e3837c 100644
--- a/SCons/utils.py
+++ b/SCons/utils.py
@@ -28,12 +28,15 @@ def AddZLib(env, platform, alias='install-utils'):
 			print 'Please specify folder of zlib for Win32 via ZLIB_W32'
 			Exit(1)
 
-	conf = env.Configure()
-	if not conf.CheckLibWithHeader(zlib, 'zlib.h', 'c'):
-		print 'zlib (%s) is missing!' % (platform)
-		Exit(1)
+	# Avoid unnecessary configuring when cleaning targets 
+	# and a clash when scons is run in parallel operation.
+	if not env.GetOption('clean'):
+		conf = env.Configure()
+		if not conf.CheckLibWithHeader(zlib, 'zlib.h', 'c'):
+			print 'zlib (%s) is missing!' % (platform)
+			Exit(1)
 
-	env = conf.Finish()
+		env = conf.Finish()
 
 
 def GetAvailableLibs(env, libs):