COMPILE_ONLY in bcm_test should use object library

[pfultz2]

See this comment from @eldiener:

Why not have the line:

add_library(${PARSE_NAME} STATIC EXCLUDE_FROM_ALL ${SOURCES})

be instead:

add_library(${PARSE_NAME} OBJECT EXCLUDE_FROM_ALL ${SOURCES})

if it works. This would allow just the creation of object files rather than the creation of a static library, which is overkill in this situation.