feat: update FAQ about rpath/runpath

adtools-light/adtools/cmake/CMakeListsPub.cmake

@@ -252,6 +252,24 @@ else ()
     set (LIB_EXT_STR ".a")
     set (EXE_EXT_STR "")
 
+    # NOTE(anjingyu):
+    # If you want to append or change the rpath/runpath, you have three ways:
+    #
+    # 1. target_link_options, RECOMMENDED
+    # target_link_options (${TARGET_NAME}
+    #     PRIVATE "-Wl,-rpath,$ORIGIN")
+    #
+    # 2. set_target_properties with LINK_FLAGS, NOT LINK_OPTIONS,
+    #    because the LINK_OPTIONS will overwrite all the link flags.
+    # set_target_properties (${TEST_TARGET_NAME} PROPERTIES
+    #     LINK_FLAGS "-Wl,-rpath,$ORIGIN")
+    #
+    # 3. set_target_properties with `SKIP_BUILD_RPATH OFF` and BUILD_RPATH,
+    #    this has a side effect: will introduce all the link_directories into
+    #    your rpath/runpath, them are appended by CMake automatically.
+    # set_target_properties (${TEST_TARGET_NAME} PROPERTIES
+    #     SKIP_BUILD_RPATH OFF
+    #     BUILD_RPATH "$ORIGIN/lib")
     if (NOT ADMAKE_ENABLE_BUILD_RPATH)
         set (CMAKE_SKIP_BUILD_RPATH TRUE)
     endif ()

adtools-light/docs/faq.md

@@ -123,3 +123,30 @@ NEXUS_HOST=http:://repository:1804 admake build
 NEXUS_HOST=http:://repository:1804 admake fetch protobuf
 ```
 
+### How to append or change `rpath/runpath` (Unix ONLY)?
+
+By default, `admake` will disable the `rpath` globally via `set (CMAKE_SKIP_BUILD_RPATH TRUE)`, so you will get clean `Shared Objects` or `ELFs`.
+
+If you want to append or change the `rpath/runpath`, you have three ways:
+
+1. `target_link_options`, *RECOMMENDED*:
+    ``` cmake
+    target_link_options (${TARGET_NAME}
+        PRIVATE "-Wl,-rpath,$ORIGIN")
+    ```
+2. `set_target_properties` with `LINK_FLAGS`, **NOT** `LINK_OPTIONS`,
+   because the `LINK_OPTIONS` will overwrite all the link flags.
+
+    ``` cmake
+    set_target_properties (${TEST_TARGET_NAME} PROPERTIES
+        LINK_FLAGS "-Wl,-rpath,$ORIGIN")
+    ```
+3. `set_target_properties` with `SKIP_BUILD_RPATH OFF` and `BUILD_RPATH`,
+   this has a side effect: will introduce all the `link_directories` into
+   your `rpath/runpath`, them are appended by CMake automatically.
+    ``` cmake
+    set_target_properties (${TEST_TARGET_NAME} PROPERTIES
+        SKIP_BUILD_RPATH OFF
+        BUILD_RPATH "$ORIGIN")
+    ```
+