查找库所在目录FIND_LIBRARY

语法：

find_library (
          <VAR>
          name | NAMES name1 [name2 ...] [NAMES_PER_DIR]
          [HINTS path1 [path2 ... ENV var]]
          [PATHS path1 [path2 ... ENV var]]
          [PATH_SUFFIXES suffix1 [suffix2 ...]]
          [DOC "cache documentation string"]
          [NO_DEFAULT_PATH]
          [NO_CMAKE_ENVIRONMENT_PATH]
          [NO_CMAKE_PATH]
          [NO_SYSTEM_ENVIRONMENT_PATH]
          [NO_CMAKE_SYSTEM_PATH]
          [CMAKE_FIND_ROOT_PATH_BOTH |
           ONLY_CMAKE_FIND_ROOT_PATH |
           NO_CMAKE_FIND_ROOT_PATH]
         )

例子如下：

FIND_LIBRARY(RUNTIME_LIB mylib /usr/lib  /usr/local/lib NO_DEFAULT_PATH)

cmake会在目录中查找，如果所有目录中都没有，值RUNTIME_LIB就会被赋为NO_DEFAULT_PATH