Regenerate if cross build definition file is updated.

backends.py

@@ -861,6 +861,9 @@ class NinjaBackend(Backend):
 
         deps = [os.path.join(self.build_to_src, df) \
                 for df in self.interpreter.get_build_def_files()]
+        if self.environment.is_cross_build():
+            deps.append(os.path.join(self.build_to_src,
+                                     self.environment.coredata.cross_file))
         elem = NinjaBuildElement('build.ninja', 'REGENERATE_BUILD', deps)
         elem.write(outfile)
 

coredata.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import pickle
+import pickle, os
 
 version = '0.7.0-research'
 
@@ -34,7 +34,10 @@ class CoreData():
         self.buildtype = options.buildtype
         self.strip = options.strip
         self.coverage = options.coverage
-        self.cross_file = options.cross_file
+        if options.cross_file is not None:
+            self.cross_file = os.path.join(os.getcwd(), options.cross_file)
+        else:
+            self.cross_file = None
 
         self.compilers = {}
         self.deps = {}

environment.py

@@ -695,7 +695,7 @@ class Environment():
         try:
             cdf = os.path.join(self.get_build_dir(), Environment.coredata_file)
             self.coredata = coredata.load(cdf)
-        except IOError:
+        except FileNotFoundError:
             self.coredata = coredata.CoreData(options)
         if self.coredata.cross_file:
             self.cross_info = CrossBuildInfo(self.coredata.cross_file)