Prevent headers to be regenerated from IDL

Fixes build failure when the environment variable WIDL is set
(which happens automatically when mingw-w64-tools is installed)

mingw-headers-no-widl.patch

@@ -0,0 +1,22 @@
+--- mingw-w64-headers/configure.ac.orig	2014-03-30 15:23:08.248186613 +0200
++++ mingw-w64-headers/configure.ac	2014-03-30 15:24:15.775316204 +0200
+@@ -27,7 +27,7 @@
+   [AS_VAR_SET([with_widl],[no])])
+ AC_MSG_RESULT([$with_widl])
+ 
+-AS_VAR_IF([with_widl],[no],[],[
++AS_VAR_IF([with_widl],[no],[unset WIDL],[
+   AS_VAR_IF([srcdir],[.],[],
+     [AC_MSG_WARN([--with-widl used in out of the tree compilation.  Existing generated files will not be modified.])])
+   AC_PATH_PROGS([WIDL], [$host-widl widl], [], [$with_widl])
+--- mingw-w64-headers/configure.orig	2014-03-30 15:24:23.969453233 +0200
++++ mingw-w64-headers/configure	2014-03-30 15:24:26.479495205 +0200
+@@ -2565,7 +2473,7 @@
+ $as_echo "$with_widl" >&6; }
+ 
+ if test "x$with_widl" = xno; then :
+-
++  unset WIDL
+ else
+ 
+   if test "x$srcdir" = x.; then :

mingw-headers.spec

@@ -37,6 +37,12 @@ Source0:        http://sourceforge.net/code-snapshots/svn/m/mi/mingw-w64/code/mi
 Source0:        http://downloads.sourceforge.net/mingw-w64/mingw-w64-v%{version}.tar.bz2
 %endif
 
+# Our RPM macros automatically set the environment variable WIDL
+# This confuses the mingw-headers configure scripts and causes various
+# headers to be regenerated from their .idl source. Prevent this from
+# happening as the .idl files shouldn't be used by default
+Patch0:         mingw-headers-no-widl.patch
+
 BuildArch:      noarch
 
 BuildRequires:  mingw32-filesystem >= 95
@@ -82,6 +88,8 @@ unzip %{S:0}
 %setup -q -n mingw-w64-v%{version}
 %endif
 
+%patch0 -p0 -b .idl
+
 
 %build
 pushd mingw-w64-headers
@@ -117,6 +125,9 @@ rm -f $RPM_BUILD_ROOT%{mingw64_includedir}/pthread_unistd.h
 %changelog
 * Sun Mar 30 2014 Erik van Pienbroek <epienbro@fedoraproject.org> - 3.1.999-0.8.trunk.r6559.20140330
 - Update to r6559 (20140330 snapshot)
+- Prevent headers to be regenerated from IDL
+  Fixes build failure when the environment variable WIDL is set
+  (which happens automatically when mingw-w64-tools is installed)
 
 * Mon Feb 24 2014 Erik van Pienbroek <epienbro@fedoraproject.org> - 3.1.999-0.7.trunk.r6497.20140224
 - Update to r6497 (20140224 snapshot)