Fix rocksdb cmake depends should use list instead of string (apache#518)

Author: git-hulk

README.md

@@ -53,8 +53,9 @@ Kvrocks has the following key features:
 # Centos/Redhat
 sudo yum install -y epel-release && sudo yum install -y git gcc gcc-c++ make snappy snappy-devel autoconf automake libtool which gtest gtest-devel
 
-# Ubuntu
-sudo apt-get install gcc g++ make libsnappy-dev autoconf automake libtool which libgtest-dev
+# Ubuntu/Debian
+sudo apt update
+sudo apt-get install gcc g++ make libsnappy-dev autoconf automake libtool
 
 # MACOSX
 brew install autoconf automake libtool snappy googletest

cmake/rocksdb.cmake

@@ -16,7 +16,8 @@ if (NOT __ROCKSDB_INCLUDED)
   set(ROCKSDB_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${ROCKSDB_EXTRA_COMPILER_FLAGS}")
   set(ROCKSDB_C_FLAGS "${CMAKE_C_FLAGS} ${ROCKSDB_EXTRA_COMPILER_FLAGS}")
   if (NOT DISABLE_JEMALLOC)
-    set(ROCKSDB_DEPENDS "jemalloc snappy")
+    list(APPEND rocksdb_DEPENDS jemalloc)
+    list(APPEND rocksdb_DEPENDS snappy)
     set(JEMALLOC_ROOT_DIR ${jemalloc_INSTALL})
   else()
     set(rocksdb_DEPENDS "snappy")