CMakeLists.txt attempts to use undefined variable `_BUILD_VERSION`

[Michael Jones]

string(FIND ${BUILD_VERSION} / BUILD_VERSION_POS REVERSE)
if(BUILD_VERSION_POS GREATER -1)
    math(EXPR BUILD_VERSION_POS "${BUILD_VERSION_POS} + 1")
    string(SUBSTRING ${BUILD_VERSION} ${BUILD_VERSION_POS} -1 BUILD_VERSION)
endif()
message("BUILD_VERSION:${BUILD_VERSION};${_BUILD_VERSION}")
set(VERSION ${BUILD_VERSION})

See the second to last line in the code snip above.