lzma2 on freearc as external

[gozarck]

Hello panker1992 thnks for share your work.
i just add lc4 and lp0 you gain very little bytes in compression.

[External compressor:7z]
packcmd = 7z.exe a -t7z -mcrc=0 -m1=lzma2:fb=273:mf=bt4:mc=1000:lc=4:lp0 -mx9 $$arcpackedfile$$.7z $$arcdatafile$$.dll
unpackcmd = 7z.exe x -y $$arcpackedfile$$.7z $$arcdatafile$$.dll
packedfile = $$arcpackedfile$$.7z
datafile = $$arcdatafile$$.dll

if you see the code i use -t7z instead -txz because lzma2 is default compression in 7zip since 2012.
Also i inject your 7z.dll into 7z.exe check the attachment, just drag and drop any file in the bat file to test.