using _ instead of - now

hal/src/fsfw_hal/linux/CMakeLists.txt

@@ -0,0 +1,13 @@
+if(FSFW_HAL_ADD_RASPBERRY_PI)
+    add_subdirectory(rpi)
+endif()
+
+target_sources(${LIB_FSFW_NAME} PRIVATE
+	UnixFileGuard.cpp
+	utility.cpp
+)
+
+add_subdirectory(gpio)
+add_subdirectory(spi)
+add_subdirectory(i2c)
+add_subdirectory(uart)