doc: add troubleshooting entry and python notice

docs/cli.md

@@ -74,7 +74,7 @@ Building natively is a bit more advanced and not recommended for beginners
 
 4. Download and install [cmake](https://cmake.org/download/). Again, when asked, add to your path
 
-5. Download and install [python](https://www.python.org/downloads/). When asked, add to your path (small checkbox in the bottom left)
+5. Download and install [python](https://www.python.org/downloads/). When asked, add to your path (small checkbox in the bottom left). Python 3.9 or above is required.
 
 6. Choose a suitable location and open a terminal. Clone the repository with `git clone https://github.com/RfidResearchGroup/ChameleonUltra.git`
 
@@ -110,6 +110,8 @@ Install the dependencies
   - Arch:  
   `sudo pacman -S  git cmake base-devel python3`
 
+Python 3.9 or above is required.
+
 Run the following script to clone the Repository, compile the tools and install Python dependencies in a virtual environment.
 
 ```sh

docs/troubleshooting.md

@@ -82,6 +82,39 @@ pacman -R ninja --noconfirm
 pacman -S mingw-w64-x86_64-ninja --noconfirm
 ```
 
+## cmake: Undefined reference to "pthread_create"
+
+It has been reported that on some Linux systems cmake doesnt find pthread.
+
+Make sure to have libpthread installed, the package may be named differently on your distro.
+
+On ubuntu and same based systems it is the following command:
+```
+sudo apt install libpthread-stubs0-dev
+```
+
+If this doesnt fix it, you may need to set pthread in the LDFLAGS enviroment variable, this can be done by running the command with the enviroment variable at the beginning:
+
+```
+LDFLAGS=-pthread cmake ..
+```
+
+If the error still persists you may also need to provide a specific compiler version, you do that by adding the -DCMAKE_C_COMPILER argument:
+
+```
+LDFLAGS=-pthread cmake -DCMAKE_C_COMPILER=gcc-11 ..
+```
+
+The compiler needs to be installed too ofcourse, the package name may be differently on your distro.
+
+On ubuntu and same based systems its the following command:
+
+```
+sudo apt install gcc-11 g++-11
+```
+
+The following ```cmake --build . --config Release``` should work again without modification.
+
 # CLI usage
 
 ## InvalidException: Device unsupported cmd