add dirty hack for linux build in howto build-linux.txt

Author: q4a

doc/howto/build-linux.txt

@@ -22,6 +22,8 @@ Build commands:
 ------
 cd xray-16
 git submodule update --init --recursive
+//temporary fix is removing cryptopp
+rm -rf Externals/cryptopp/*
 mkdir bin && cd bin
 cmake ..
 (or export CC=clang && export CXX=clang++ && cmake ..)