Fix system cityhash setup

cityhash does not provide any CMake packages, so it cannot be imported
with `find_package` or used with the alias `cityhash::cityhash`.

To fix that, we need the following:
1. Use `find_library` to find the `cityhash` library.
2. Remove the `cityhash::cityhash` alias, and use plain `cityhash` to
refer to the library.

Signed-off-by: Ruoyu Zhong <[email protected]>

Author: ZhongRuoyu

CMakeLists.txt

@@ -77,7 +77,7 @@ PROJECT (CLICKHOUSE-CLIENT)
     ENDIF ()
 
     IF (WITH_SYSTEM_CITYHASH)
-        FIND_PACKAGE(cityhash REQUIRED)
+        FIND_LIBRARY(SYSTEM_CITYHASH NAMES cityhash REQUIRED)
     ELSE ()
         INCLUDE_DIRECTORIES (contrib/cityhash/cityhash)
         SUBDIRS (contrib/cityhash/cityhash)

clickhouse/CMakeLists.txt

@@ -42,7 +42,7 @@ ADD_LIBRARY (clickhouse-cpp-lib ${clickhouse-cpp-lib-src})
 SET_TARGET_PROPERTIES (clickhouse-cpp-lib PROPERTIES LINKER_LANGUAGE CXX)
 TARGET_LINK_LIBRARIES (clickhouse-cpp-lib
     absl::int128
-    cityhash::cityhash
+    cityhash
     lz4::lz4
 )
 TARGET_INCLUDE_DIRECTORIES (clickhouse-cpp-lib

contrib/cityhash/cityhash/CMakeLists.txt

@@ -3,5 +3,3 @@ ADD_LIBRARY (cityhash STATIC
 )
 
 set_property(TARGET cityhash PROPERTY POSITION_INDEPENDENT_CODE ON)
-
-ADD_LIBRARY (cityhash::cityhash ALIAS cityhash)