scons: Pass few envvars to the build env to fix mingw-gcc

scons/PKGBUILD

@@ -2,21 +2,27 @@
 
 pkgname=scons
 pkgver=2.3.4
-pkgrel=2
+pkgrel=3
 pkgdesc="Extensible Python-based build utility"
 arch=('any')
 groups=('base-devel')
 url="http://scons.org"
 license=('MIT')
 depends=('python2')
 source=("http://downloads.sourceforge.net/sourceforge/$pkgname/$pkgname-$pkgver.tar.gz"
-        scons-2.3.4-cyglink-msys2.patch)
+        scons-2.3.4-cyglink-msys2.patch
+        scons-2.3.4-msys2-plat-mingw-env.patch)
 md5sums=('91fbbb67c2c65b03c746601baac4a6a5'
-         '8449f7f389bdd54f07d8ab27a8b7b48f')
+         '8449f7f389bdd54f07d8ab27a8b7b48f'
+         '4eb3a62a2fff6cac1cccd45a21cbcd8a')
 
 prepare() {
   cd "$srcdir/$pkgname-$pkgver"
+
+  # avoid errors when re-running makepkg
+  rm -f engine/SCons/Platform/msys.py engine/SCons/Tool/msyslink.py
   patch -p1 -i ${srcdir}/scons-2.3.4-cyglink-msys2.patch
+  patch -p0 -i ${srcdir}/scons-2.3.4-msys2-plat-mingw-env.patch
 }
 
 package() {

scons/scons-2.3.4-msys2-plat-mingw-env.patch

@@ -0,0 +1,24 @@
+--- engine/SCons/Platform/msys.py.orig	2015-05-06 15:26:45.478712800 +0200
++++ engine/SCons/Platform/msys.py	2015-05-06 15:33:07.915575600 +0200
+@@ -38,6 +38,21 @@
+ def generate(env):
+     posix.generate(env)
+
++    # (copied from win32.py, for when msys2 scons is used for building mingw packages)
++    # Import things from the external environment to the construction
++    # environment's ENV.  This is a potential slippery slope, because we
++    # *don't* want to make builds dependent on the user's environment by
++    # default.  We're doing this for SystemRoot, though, because it's
++    # needed for anything that uses sockets, and seldom changes, and
++    # for SystemDrive because it's related.
++    #
++    # Weigh the impact carefully before adding other variables to this list.
++    import_env = [ 'SystemDrive', 'SystemRoot', 'TEMP', 'TMP' ]
++    for var in import_env:
++        v = os.environ.get(var)
++        if v:
++            env['ENV'][var] = v
++
+     env['ENV']['PATH'] = os.getenv('PATH')
+     env['SPAWN']       = (lambda sh, esc, cmd, args, env_param:
+                           subprocess.call(['sh', '-c', ' '.join(args)]))