Don't build a shared library on Windows.

Change-Id: Ia3f3957d5f63f5e99e31a84367bb1507fef6618d

internal/ceres/CMakeLists.txt

diff --git a/internal/ceres/CMakeLists.txt b/internal/ceres/CMakeLists.txt
index f2fc827..2914601 100644
--- a/internal/ceres/CMakeLists.txt
+++ b/internal/ceres/CMakeLists.txt
@@ -148,11 +148,15 @@
 ADD_LIBRARY(ceres STATIC ${CERES_LIBRARY_SOURCE})
 TARGET_LINK_LIBRARIES(ceres ${CERES_LIBRARY_DEPENDENCIES})
 
-ADD_LIBRARY(ceres_shared SHARED ${CERES_LIBRARY_SOURCE})
-TARGET_LINK_LIBRARIES(ceres_shared ${CERES_LIBRARY_DEPENDENCIES})
-SET_TARGET_PROPERTIES(ceres_shared PROPERTIES
-    VERSION ${CERES_VERSION}
-    SOVERSION ${CERES_ABI_VERSION})
+# Don't build a DLL on MSVC. Supporting Ceres as a DLL on Windows involves
+# nontrivial changes that we haven't made yet.
+IF (NOT MSVC)
+  ADD_LIBRARY(ceres_shared SHARED ${CERES_LIBRARY_SOURCE})
+  TARGET_LINK_LIBRARIES(ceres_shared ${CERES_LIBRARY_DEPENDENCIES})
+  SET_TARGET_PROPERTIES(ceres_shared PROPERTIES
+      VERSION ${CERES_VERSION}
+      SOVERSION ${CERES_ABI_VERSION})
+ENDIF (NOT MSVC)
 
 IF (${BUILD_TESTING})
   ADD_LIBRARY(gtest gmock_gtest_all.cc gmock_main.cc)