added full crosstool-ng instructions

CMakeLists.txt

@@ -164,7 +164,7 @@ endif()
 
 string(CONCAT POST_BUILD_COMMENT
     "Build directory: ${CMAKE_BINARY_DIR}\n"
-    "Target OSAL: ${OS_FSFW}\n"
+    "Target OSAL: ${FSFW_OSAL}\n"
     "Target Build Type: ${CMAKE_BUILD_TYPE}\n"
     "${TARGET_STRING}"
 )

cmake/BBBCrossCompileConfig.cmake

@@ -33,6 +33,15 @@ else()
 	)
 endif()
 
+# Generally, the debian roots will be a multiarch rootfs where some libraries are put
+# into a folder named "arm-linux-gnueabihf". The user can override the folder name if this is
+# not the case
+if(NOT ENV{MULTIARCH_FOLDER_NAME})
+    set(MULTIARCH_FOLDER_NAME "arm-linux-gnueabihf")
+else()
+    set(MUTLIARCH_FOLDER_NAME $ENV{MULTIARCH_FOLDER_NAME})
+endif()
+
 message(STATUS "Using sysroot path: ${SYSROOT_PATH}")
 
 set(CROSS_COMPILE_CC "${CROSS_COMPILE}-gcc")
@@ -62,9 +71,9 @@ set(CMAKE_SYSTEM_PROCESSOR "arm")
 # List of library dirs where LD has to look. Pass them directly through gcc. 
 # LD_LIBRARY_PATH is not evaluated by arm-*-ld
 set(LIB_DIRS 
-	"${SYSROOT_PATH}/lib/${CROSS_COMPILE}"
+	"${SYSROOT_PATH}/lib/${MUTLIARCH_FOLDER_NAME}"
 	"${SYSROOT_PATH}/usr/local/lib"
-	"${SYSROOT_PATH}/usr/lib/${CROSS_COMPILE}"
+	"${SYSROOT_PATH}/usr/lib/${MUTLIARCH_FOLDER_NAME}"
 	"${SYSROOT_PATH}/usr/lib"
 )
 # You can additionally check the linker paths if you add the 
@@ -74,11 +83,6 @@ foreach(LIB ${LIB_DIRS})
 	set(COMMON_FLAGS "${COMMON_FLAGS} -L${LIB} -Wl,-rpath-link,${LIB}")
 endforeach()
 
-set(CMAKE_PREFIX_PATH 
-	"${CMAKE_PREFIX_PATH}"
-	"${SYSROOT_PATH}/usr/lib/${CROSS_COMPILE}"
-)
-
 set(CMAKE_C_FLAGS 
 	"-march=armv7-a -mtune=cortex-a8 -mfpu=neon -mfloat-abi=hard ${COMMON_FLAGS}" 
 	CACHE STRING "Flags for Beagle Bone Black"

doc/README-rpi.md

@@ -440,13 +440,14 @@ scp <user_name>@<ip-address>:/lib/arm-linux-gnueabihf/libc.so.6 <rootfs_path>/li
 If any custom libraries are used which rely on symlinks, it might be necessary to copy them
 or create them manually as well.
 
-# <a id="ctng"></a> Building a cross-compile toolchain with crosstool-ng
+# <a id="ctng"></a> Building a cross-compile toolchain with `crosstool-ng`
 
 If you want to cross-compile the toolchain for the Raspberry Pi, you can do so
 with the `crosstool-ng` tool.
 
 Alternatively, you can also download a cross-compile toolchain built with
-crosstool-ng for the Raspberry Pi 3 [from here](https://www.dropbox.com/sh/zjaex4wlv5kcm6q/AAABBFfmZSRZ7GE7ok-7vTE6a?dl=0)
+crosstool-ng for the Raspberry Pi 3 and the Raspbery Pi 4 
+[from here](https://www.dropbox.com/sh/zjaex4wlv5kcm6q/AAABBFfmZSRZ7GE7ok-7vTE6a?dl=0)
 inside the `x-tools` folder.
 
 ## Ubuntu
@@ -474,8 +475,8 @@ inside the `x-tools` folder.
    sudo make install
    ```
 
-   You can also install `ct-ng` locally by supplying `--prefix=<installPath>` to the `configure` 
-   command. You don't need `sudo` for the `make install` command if you do this
+   You can also install `ct-ng` locally by replacing `--enable-local` with `--prefix=<installPath>`
+   to the `configure`  command. You don't need `sudo` for the `make install` command if you do this.
 
 4. You can get a list of architectures by running 
 
@@ -506,7 +507,20 @@ inside the `x-tools` folder.
    It is recommended to go to `Paths and misc options` and disable `Paths and misc options`.
    Remember to save the configuration.
 
-5. Finally, after finishing the configuration you can build the toolchain with
+5. The correct configuration files for the Raspberry Pi 3 and Raspberry Pi 4 are provided here
+   are were set up according to [these instructions](https://medium.com/@stonepreston/how-to-cross-compile-a-cmake-c-application-for-the-raspberry-pi-4-on-ubuntu-20-04-bac6735d36df).
+   You can download those files from [here](https://www.dropbox.com/sh/ok554i453phuqec/AACcv-fxpIXi3Nh1z8UWu4Sea?dl=0).
+
+   Put the `patches` folder, the `.config` folder and the `env.sh` in the same directory where
+   you run `ct-ng`. After that, you can check the configuration with `./ct-ng menuconfig`.
+
+   Set up the multiarch environment for debian by running
+
+   ```sh
+   . env.sh
+   ```
+
+6. Finally, after finishing the configuration you can build the toolchain with
 
    ```sh
    ./ct-ng build
@@ -514,3 +528,17 @@ inside the `x-tools` folder.
 
    This takes 20-30 minutes. You can find the toolchain in the `~/x-tools` folder after building
    has finished
+
+7. You can check whether the toolchain was configured correctly for multiarch by running the
+   following command
+
+   ```sh
+   cd ~/x-tools/armv8-rpi3-linux-gnueabihf/armv8-rpi3-linux-gnueabihf/bin
+   ./ld --verbose | grep -i "search"
+   ```
+
+   The output should include
+
+   ```sh
+   SEARCH_DIR("=/lib/arm-linux-gnueabihf"); SEARCH_DIR("=/usr/lib/arm-linux-gnueabihf");
+   ```