Duplicated `Resources/unity_builtin_extra` in every asset bundles.

Hi, i’m building my game with asset bundles. And i just found that every asset bundle that compiled with BuildPipeline.BuildAssetBundles will contains a copy of Resources/unity_builtin_extra. Is this the default behavior? Do i have any chance to get rid of it ?

Bundle Name: sa_character_femalepyro.prefab
Compressed Size:98.7 kb
Uncompressed usage by category:
Textures      32.2 kb	 13.7% 
Meshes        0.0 kb	 0.0% 
Animations    0.0 kb	 0.0% 
Sounds        0.0 kb	 0.0% 
Shaders       119.2 kb	 50.7% 
Other Assets  37.5 kb	 15.9% 
Levels        0.0 kb	 0.0% 
Scripts       0.0 kb	 0.0% 
Included DLLs 0.0 kb	 0.0% 
File headers  46.4 kb	 19.7% 
Complete size 235.3 kb	 100.0% 

Used Assets and files from the Resources folder, sorted by uncompressed size:
 120.3 kb	 51.1% Resources/unity_builtin_extra
 32.2 kb	 13.7% Assets/PrestreamingAssets/Characters/_Textures/Characters/SA_Character_FemalePyro.png
 31.8 kb	 13.5% Assets/PrestreamingAssets/Characters/_Prefabs/Characters/SA_Character_FemalePyro.prefab
 3.6 kb	 1.5% AssetBundle Object
 0.9 kb	 0.4% Assets/PrestreamingAssets/Characters/_Materials/Characters/SA_Character_FemalePyro.mat
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Bundle Name: sa_character_femalesoldier.prefab
Compressed Size:124.3 kb
Uncompressed usage by category:
Textures      32.2 kb	 11.6% 
Meshes        0.0 kb	 0.0% 
Animations    0.0 kb	 0.0% 
Sounds        0.0 kb	 0.0% 
Shaders       161.3 kb	 58.1% 
Other Assets  37.5 kb	 13.5% 
Levels        0.0 kb	 0.0% 
Scripts       0.0 kb	 0.0% 
Included DLLs 0.0 kb	 0.0% 
File headers  46.4 kb	 16.7% 
Complete size 277.4 kb	 100.0% 

Used Assets and files from the Resources folder, sorted by uncompressed size:
 162.4 kb	 58.5% Resources/unity_builtin_extra
 32.2 kb	 11.6% Assets/PrestreamingAssets/Characters/_Textures/Characters/SA_Character_FemaleSoldier.png
 31.8 kb	 11.5% Assets/PrestreamingAssets/Characters/_Prefabs/Characters/SA_Character_FemaleSoldier.prefab
 3.6 kb	 1.3% AssetBundle Object
 1.0 kb	 0.3% Assets/PrestreamingAssets/Characters/_Materials/Characters/SA_Character_FemaleSoldier.mat

There is an article which solved this problem, but it is written in Chinese Simplified. If you want to browse it you could use Google Chrome to visit and translate it to your language.

Unity 5.x AssetBundle零冗余解决方案 - 知乎 posted on 2017-02-08