build: Hold an identifier for the host the package is built on

This can be changed using build_host option in pisi.conf. The
default value is "localhost". This can be used to distinguish
buildfarm packages and the packages built by the user.

pisi/configfile.py

@@ -80,6 +80,7 @@ class GeneralDefaults:
 
 class BuildDefaults:
     """Default values for [build] section"""
+    build_host = "localhost"
     host = "i686-pc-linux-gnu"
     jobs = "-j3"
     generateDebug = False

pisi/metadata.py

@@ -46,6 +46,7 @@ class Package(specfile.Package, xmlfile.XmlFile):
     __metaclass__ = autoxml.autoxml
 
     t_Build = [ autoxml.Integer, autoxml.optional]
+    t_BuildHost = [autoxml.String, autoxml.optional]
     t_Distribution = [ autoxml.String, autoxml.mandatory]
     t_DistributionRelease = [ autoxml.String, autoxml.mandatory]
     t_Architecture = [ autoxml.String, autoxml.mandatory]

pisi/operations/build.py

@@ -831,6 +831,8 @@ class Builder:
         metadata = pisi.metadata.MetaData()
         metadata.from_spec(self.spec.source, package, self.spec.history)
 
+        metadata.package.buildHost = ctx.config.values.build.build_host
+
         metadata.package.distribution = ctx.config.values.general.distribution
         metadata.package.distributionRelease = ctx.config.values.general.distribution_release
         metadata.package.architecture = ctx.config.values.general.architecture