cmake: fix destination path (#34)

`share/${GROONGA_NORMALIZER_MYSQL_PROJECT_NAME}` is shown
`share/groonga-normalizer-mysql`.
Thus, `README.md` and `doc/text/lgpl-2.0.txt`are installed in
`share/groonga-normalizer-mysql/`.
However, these files are installed `share/doc/groonga-normalizer-mysql/`
for RPM packages.

See:
https://github.com/groonga/groonga-normalizer-mysql/blob/main/packages/yum/groonga-normalizer-mysql.spec.in#L59C1-L59C42

I change destination path `share/groonga-normalizer-mysql` to
`share/doc/groonga-normalizer-mysql`.

---


https://github.com/groonga/groonga-normalizer-mysql/blob/main/CMakeLists.txt#L97
is defined `DESTINATION "${CMAKE_LIBDIR}/pkgconfig/"`.
However, `CMAKE_LIBDIR` is not definition. (Probably, `CMAKE_LIBDIR` is
null.)
Thus, `groonga-normalizer-mysql.pc` is installed to `pkgconfig/`. This
install path is not expected.

I change destination path `pkgconfig/` to `usr/lib64(or lib)/pkgconfig`.

CMakeLists.txt

@@ -21,9 +21,11 @@ cmake_minimum_required(VERSION 3.16)
 set(GROONGA_NORMALIZER_MYSQL_PROJECT_NAME "groonga-normalizer-mysql")
 project("${GROONGA_NORMALIZER_MYSQL_PROJECT_NAME}")
 
-if(NOT DEFINED GROONGA_NORMALIZER_MYSQL_DATA_DIR)
-  set(GROONGA_NORMALIZER_MYSQL_DATA_DIR
-    "share/${GROONGA_NORMALIZER_MYSQL_PROJECT_NAME}")
+include(GNUInstallDirs)
+
+if(NOT DEFINED GROONGA_NORMALIZER_MYSQL_DOC_DIR)
+  set(GROONGA_NORMALIZER_MYSQL_DOC_DIR
+    "${CMAKE_INSTALL_DOCDIR}/${GROONGA_NORMALIZER_MYSQL_PROJECT_NAME}")
 endif()
 
 if(DEFINED GROONGA_NORMALIZER_MYSQL_EMBED)
@@ -94,10 +96,10 @@ if(NOT GROONGA_NORMALIZER_MYSQL_EMBED)
     @ONLY)
   install(
     FILES "${CMAKE_CURRENT_BINARY_DIR}/groonga-normalizer-mysql.pc"
-    DESTINATION "${CMAKE_LIBDIR}/pkgconfig/")
+    DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig/")
 endif()
 
 install(FILES
   "README.md"
   "doc/text/lgpl-2.0.txt"
-  DESTINATION "${GROONGA_NORMALIZER_MYSQL_DATA_DIR}")
+  DESTINATION "${GROONGA_NORMALIZER_MYSQL_DOC_DIR}")