Rather than exclude the entire library from non mono arches just don't build the bindings

libappindicator.spec

@@ -1,6 +1,6 @@
 Name:		libappindicator
 Version:	12.10.0
-Release:	7%{?dist}
+Release:	8%{?dist}
 Summary:	Application indicators library
 
 Group:		System Environment/Libraries
@@ -17,19 +17,19 @@ BuildRequires:	dbus-glib-devel
 BuildRequires:	libdbusmenu-devel
 BuildRequires:	libdbusmenu-gtk2-devel
 BuildRequires:	libdbusmenu-gtk3-devel
-BuildRequires:	gtk-sharp2-gapi
 BuildRequires:	gobject-introspection-devel
 BuildRequires:	gtk2-devel
 BuildRequires:	gtk3-devel
-BuildRequires:	gtk-sharp2-devel
 BuildRequires:	libindicator-devel
 BuildRequires:	libindicator-gtk3-devel
-BuildRequires:	mono-devel
-BuildRequires:	mono-nunit-devel
 BuildRequires:	python2-devel
 BuildRequires:	pygtk2-devel
-
+%ifarch %{mono_arches}
-ExclusiveArch:	%{mono_arches}
+BuildRequires:	gtk-sharp2-devel
+BuildRequires:	gtk-sharp2-gapi
+BuildRequires:	mono-devel
+BuildRequires:	mono-nunit-devel
+%endif
 
 %description
 A library to allow applications to export a menu into the Unity Menu bar. Based
@@ -94,6 +94,7 @@ This package contains the documentation for the appindicator and
 appindicator-gtk3 libraries.
 
 
+%ifarch %{mono_arches}
 %package sharp
 Summary:	Application indicators library - C#
 Group:		System Environment/Libraries
@@ -114,13 +115,14 @@ Requires:	%{name}-sharp = %{version}-%{release}
 
 %description sharp-devel
 This package contains the development files for the appindicator-sharp library.
+%endif
 
 
 %prep
 %setup -q
 %patch0 -p1 -b .monodir
 
-autoreconf -vfi
+autoreconf -vif
 
 
 %build
@@ -212,6 +214,7 @@ find %{buildroot} -type f -name '*.la' -delete
 %doc %{_datadir}/gtk-doc/html/libappindicator/
 
 
+%ifarch %{mono_arches}
 %files sharp
 %doc AUTHORS README COPYING COPYING.LGPL.2.1
 %dir %{_libdir}/appindicator-sharp-0.1/
@@ -237,8 +240,12 @@ find %{buildroot} -type f -name '*.la' -delete
 %files sharp-devel
 %{_libdir}/pkgconfig/appindicator-sharp-0.1.pc
 
+%endif
 
 %changelog
+* Sun Jan  4 2015 Peter Robinson <pbrobinson@fedoraproject.org> 12.10.0-8
+- Rather than exclude the entire library from non mono arches just don't build the bindings
+
 * Mon Dec 29 2014 Eduardo Echeverria  <echevemaster@gmail.com> - 12.10.0-7
 - Added workaround -Wno-deprecated-declarations for fix FTBFS