Generate fbs header file through cmake during build flow (#225)

As discussed here:
#180 (comment)

Old setup involved building the `flatc` executable and then manually
running it to generate the header file.

Now it is integrated into the cmake build flow and
`tt_simulation_device_generated.h` will be generated as a dependency of
`device` target.

cmake/dependencies.cmake

@@ -63,11 +63,30 @@ CPMAddPackage(
     GITHUB_REPOSITORY google/flatbuffers
     GIT_TAG v24.3.25
     OPTIONS
-        "FLATBUFFERS_BUILD_FLATC OFF"
+        "FLATBUFFERS_BUILD_FLATC ON"
         "FLATBUFFERS_BUILD_TESTS OFF"
         "FLATBUFFERS_SKIP_MONSTER_EXTRA ON"
         "FLATBUFFERS_STRICT_MODE ON"
 )
+function(GENERATE_FBS_HEADER FBS_FILE)
+    get_filename_component(FBS_FILE_NAME ${FBS_FILE} NAME)
+    get_filename_component(FBS_FILE_DIR ${FBS_FILE} DIRECTORY)
+    set(FBS_GENERATED_HEADER "${CMAKE_BINARY_DIR}/${FBS_FILE_NAME}_generated.h")
+    add_custom_command(
+        OUTPUT
+            ${FBS_GENERATED_HEADER}
+        COMMAND
+            flatc
+        ARGS
+            --cpp -o "${CMAKE_BINARY_DIR}/" ${FBS_FILE}
+        DEPENDS
+            flatc
+            ${FBS_FILE}
+        COMMENT "Building C++ header for ${FBS_FILE}"
+        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+    )
+    set(FBS_GENERATED_HEADER ${FBS_GENERATED_HEADER} PARENT_SCOPE)
+endfunction()
 
 ############################################################################################################################
 # libuv (for process management)

device/CMakeLists.txt

@@ -1,5 +1,7 @@
 set(POSITION_INDEPENDENT_CODE ON)
 
+GENERATE_FBS_HEADER(${PROJECT_SOURCE_DIR}/device/simulation/tt_simulation_device.fbs)
+
 set(UMD_DEVICE_SRCS
     architecture_implementation.cpp
     cpuset_lib.cpp
@@ -24,13 +26,17 @@ add_library(device SHARED ${UMD_DEVICE_SRCS})
 add_library(${PROJECT_NAME}::device ALIAS device)
 add_library(${PROJECT_NAME}_device ALIAS device) # For legacy I guess
 
+target_sources(device PRIVATE ${FBS_GENERATED_HEADER})
+
 target_include_directories(
     device
     PUBLIC
         $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>
         $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/${PROJECT_NAME}>
         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/${PROJECT_NAME}/device>
+    PRIVATE
+        $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}>
 )
 
 # flatbuffers is public - exposed to tt_metal by tt_simulation_device_generated.h