pisi should manage <ExcludeArch> tags with regex

pisi-spec.rng

@@ -175,8 +175,9 @@
     <define name="ExcludeArch">
         <element name="ExcludeArch">
             <choice>
-                <value>i686</value>
+                <value>i[3-6]86</value>
                 <value>x86_64</value>
+                <value>arm.*</value>
             </choice>
         </element>
     </define>

pisi/operations/build.py

@@ -311,8 +311,12 @@ class Builder:
     def build(self):
         """Build the package in one shot."""
 
+        # excludeArch should accept regex.
+        # eg. <exludeArch>arm.*</exludeArch> armv7l, armv5te matches
+        #     <exludeArch>i[3-6]86</exludeArch> i386, i486, i586, i686 matches
         architecture = ctx.config.values.general.architecture
-        if architecture in self.spec.source.excludeArch:
+        for arch in self.spec.source.excludeArch:
+            if re.match(arch, architecture):
                 raise ExcludedArchitectureException(
                         _("pspec.xml avoids this package from building for '%s'")
                         % architecture)