Add solver_utils.cc to Android.mk

Change-Id: I358522971711280f4362a1fa39b1568160e21e63

jni/Android.mk

diff --git a/jni/Android.mk b/jni/Android.mk
index a11833f..d64f78b 100644
--- a/jni/Android.mk
+++ b/jni/Android.mk
@@ -170,6 +170,7 @@
                    $(CERES_SRC_PATH)/schur_jacobi_preconditioner.cc \
                    $(CERES_SRC_PATH)/scratch_evaluate_preparer.cc \
                    $(CERES_SRC_PATH)/solver.cc \
+                   $(CERES_SRC_PATH)/solver_utils.cc \
                    $(CERES_SRC_PATH)/sparse_matrix.cc \
                    $(CERES_SRC_PATH)/sparse_normal_cholesky_solver.cc \
                    $(CERES_SRC_PATH)/split.cc \