Add eigen BUILD

Change-Id: Ie317326faf29898976e1048da68c0b8207a16d17
diff --git a/third_party/eigen/BUILD b/third_party/eigen/BUILD
new file mode 100644
index 0000000..fd6f889
--- /dev/null
+++ b/third_party/eigen/BUILD
@@ -0,0 +1,18 @@
+licenses(['notice'])
+
+cc_library(
+  name = 'eigen',
+  visibility = ['//visibility:public'],
+  srcs = glob(['Eigen/src/**/*.h']),
+  includes = ['.'],
+  hdrs = glob(['Eigen/*'], [
+    # Stuff that we don't have the dependencies for.
+    'Eigen/CholmodSupport',
+    'Eigen/MetisSupport',
+    'Eigen/PaStiXSupport',
+    'Eigen/PardisoSupport',
+    'Eigen/SPQRSupport',
+    'Eigen/SuperLUSupport',
+    'Eigen/UmfPackSupport',
+  ]),
+)