[1]ADD_LIBRARY: Add a library to the project using the specified source files.要求CMake根据指定的源文件生成库文件 .
•  ADD_LIBRARY(libname [SHARED | STATIC | MODULE]
[EXCLUDE_FROM_ALL]   source1 source2 ... sourceN)Adds a
library target.

SHARED, STATIC or MODULE keywords are used to set the
library type. If the keyword MODULE appears, the library type is set to
MH_BUNDLE on systems which use dyld. On systems without dyld, MODULE is
treated like SHARED. If no keywords appear as the second argument, the
type defaults to the current value of BUILD_SHARED_LIBS. If this
variable is not set, the type defaults to STATIC.

If EXCLUDE_FROM_ALL is given the target will not be built by default. It will be built only if the user explicitly builds the target or another target that requires the target depends on it.

[2]INCLUDE_DIRECTORIES: Add include directories to the build.添加查找头文件的路径
• INCLUDE_DIRECTORIES([AFTER|BEFORE] [SYSTEM] dir1 dir2 ...)Add the
given directories to those searched by the compiler for include files.
By default the directories are appended onto the current list of
directories. This default behavior can be changed by
setting CMAKE_INCLUDE_DIRECTORIES_BEFORE to ON. By using BEFORE or
AFTER you can select between appending and prepending, independent from
the default. If the SYSTEM option is given the compiler will be told
that the directories are meant as system include
directories on some platforms.

[3]LINK_DIRECTORIES: Specify directories in which to search for libraries.添加库文件的搜索路径

LINK_DIRECTORIES(directory1 directory2 ...)

[4]TARGET_LINK_LIBRARIES: Link a target to given libraries.为每个目标分别指定需要链接的库文件(指定部分目标专用的库文件)

TARGET_LINK_LIBRARIES(target library1  <debug | optimized> library2   ...)Specify a list of libraries to be linked into the specified target. The debug and optimized strings may be used to indicate that the next library listed is to be used only for that specific type of build

[5]LINK_LIBRARIES: Link libraries to all targets added later.为所有目标统一指定需要的库文件(指定所有目标都用的库文件)
  LINK_LIBRARIES(library1 <debug | optimized> library2 ...)This is
an old CMake command for linking libraries. Use TARGET_LINK_LIBRARIES
unless you have a good reason for every target to link to the same set
of libraries.

Specify a list of libraries to be linked into any following targets (typically added with the ADD_EXECUTABLE or ADD_LIBRARY calls). This command is passed down to all subdirectories. The debug and optimized strings may be used to indicate that the next library listed is to be used only for that specific type of build.