[CMake] Problem in ADD_CUSTOM_COMMAND

[Sylvain Benner]

I missed the additional quotes, the correct command is :

ADD_CUSTOM_COMMAND(TARGET vpcl POST_BUILD COMMAND copy 
"\"${vpcl_path}\"" "\"${PROJECT_SOURCE_DIR}\"" VERBATIM)

This is a common rule in CMake script, when you want to pass an 
argument, always use quotes to be sure it will not be split into several 
arguments due to spaces or some other characters.

--Sylvain

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