cmake: do not include undefind paths

for example
```
include_directories(${LEVELDB_PREFIX}/include)
```
does not make sense if `LEVELDB_PREFIX` is not defined.

Signed-off-by: Kefu Chai <kchai@redhat.com>

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2c87ffc177d48f713401678e1f01ca74d3800e73..aeb59b49ad800b00207b65de3233a207d9db4f0d 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -57,22 +57,24 @@ endif(WITH_MANPAGE)
 
 include_directories(
   ${PROJECT_BINARY_DIR}/src/include
-  ${OFED_PREFIX}/include
-  ${LEVELDB_PREFIX}/include
-  ${PROJECT_SOURCE_DIR}/src
-)
-
-link_directories(
-  ${OFED_PREFIX}/lib
-  ${LEVELDB_PREFIX}/lib
-)
+  ${PROJECT_SOURCE_DIR}/src)
+
+if(LEVELDB_PREFIX)
+  include_directories(${LEVELDB_PREFIX}/include)
+  link_directories(${LEVELDB_PREFIX}/lib)
+endif()
+
+if(OFED_PREFIX)
+  include_directories(${OFED_PREFIX}/include)
+  link_directories(${OFED_PREFIX}/lib)
+endif()
+
 if(FREEBSD)
   include_directories(/usr/local/include)
   link_directories(/usr/local/lib)
   list(APPEND CMAKE_REQUIRED_INCLUDES /usr/local/include)
 endif(FREEBSD)
 
-
 #put all the libs and binaries in one place
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)