FRCT CMake

This section of CMake stuffs:

....
# Make declaring the list shorter/nicer
SET(FP "${CMAKE_SOURCE_DIR}/graphics/rcd/")

# Output file                     Source file
LIST(APPEND RCDFILES
  ${FP}borderhighlight_8bpp64.rcd ${FP}freerct.txt
  ${FP}cornerhighlight_8bpp64.rcd ${FP}freerct.txt
  ${FP}groundtile_8bpp64.rcd      ${FP}freerct.txt
  ${FP}people_animation.rcd       ${FP}freerct.txt
  ${FP}path_8bpp64.rcd            ${FP}paths.txt
  ${FP}shops.rcd                  ${FP}shops.txt
  ${FP}gui.rcd                    ${FP}gui.txt
  ${FP}tracks.rcd                 ${FP}tracks.txt
)

LIST(LENGTH RCDFILES RCDFILES_LENGTH)
math(EXPR RCDFILES_LENGTH_DIV_2 "${RCDFILES_LENGTH} / 2 - 1")

FOREACH(RCDFILE RANGE ${RCDFILES_LENGTH_DIV_2})
    math(EXPR INDEX_1 "${RCDFILE} * 2")
    math(EXPR INDEX_2 "${INDEX_1} + 1")
    LIST(GET RCDFILES ${INDEX_1} OUTFILE)
    LIST(GET RCDFILES ${INDEX_2} SRCFILE)

    ADD_CUSTOM_COMMAND(
          OUTPUT ${OUTFILE}
          COMMAND ${RCDGEN_EXE} ${SRCFILE}
          COMMENT "Generating rcd files from ${SRCFILE}"
          MAIN_DEPENDENCY ${SRCFILE}
    )
    message("adding ${OUTFILE}")

    LIST(APPEND OUTFILES ${OUTFILE})
ENDFOREACH(RCDFILE)

add_custom_target(rcd ALL DEPENDS ${OUTFILES})
....


Generates this gnu/make stuffs:

....
graphics/rcd/CMakeFiles/rcd: graphics/rcd/borderhighlight_8bpp64.rcd
graphics/rcd/CMakeFiles/rcd: graphics/rcd/cornerhighlight_8bpp64.rcd
graphics/rcd/CMakeFiles/rcd: graphics/rcd/groundtile_8bpp64.rcd
graphics/rcd/CMakeFiles/rcd: graphics/rcd/people_animation.rcd
graphics/rcd/CMakeFiles/rcd: graphics/rcd/path_8bpp64.rcd
graphics/rcd/CMakeFiles/rcd: graphics/rcd/shops.rcd
graphics/rcd/CMakeFiles/rcd: graphics/rcd/gui.rcd
graphics/rcd/CMakeFiles/rcd: graphics/rcd/tracks.rcd

graphics/rcd/borderhighlight_8bpp64.rcd: graphics/rcd/freerct.txt
    $(CMAKE_COMMAND) -E cmake_progress_report /home/lordaro/coding/freerct.hg/CMakeFiles $(CMAKE_PROGRESS_1)
    @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --blue --bold "Generating rcd files from /home/lordaro/coding/freerct.hg/graphics/rcd/freerct.txt"
    cd /home/lordaro/coding/freerct.hg/graphics/rcd && ../../src/rcdgen/rcdgen /home/lordaro/coding/freerct.hg/graphics/rcd/freerct.txt

graphics/rcd/path_8bpp64.rcd: graphics/rcd/paths.txt
    $(CMAKE_COMMAND) -E cmake_progress_report /home/lordaro/coding/freerct.hg/CMakeFiles $(CMAKE_PROGRESS_2)
    @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --blue --bold "Generating rcd files from /home/lordaro/coding/freerct.hg/graphics/rcd/paths.txt"
    cd /home/lordaro/coding/freerct.hg/graphics/rcd && ../../src/rcdgen/rcdgen /home/lordaro/coding/freerct.hg/graphics/rcd/paths.txt

graphics/rcd/shops.rcd: graphics/rcd/shops.txt
    $(CMAKE_COMMAND) -E cmake_progress_report /home/lordaro/coding/freerct.hg/CMakeFiles $(CMAKE_PROGRESS_3)
    @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --blue --bold "Generating rcd files from /home/lordaro/coding/freerct.hg/graphics/rcd/shops.txt"
    cd /home/lordaro/coding/freerct.hg/graphics/rcd && ../../src/rcdgen/rcdgen /home/lordaro/coding/freerct.hg/graphics/rcd/shops.txt

graphics/rcd/gui.rcd: graphics/rcd/gui.txt
    $(CMAKE_COMMAND) -E cmake_progress_report /home/lordaro/coding/freerct.hg/CMakeFiles $(CMAKE_PROGRESS_4)
    @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --blue --bold "Generating rcd files from /home/lordaro/coding/freerct.hg/graphics/rcd/gui.txt"
    cd /home/lordaro/coding/freerct.hg/graphics/rcd && ../../src/rcdgen/rcdgen /home/lordaro/coding/freerct.hg/graphics/rcd/gui.txt

graphics/rcd/tracks.rcd: graphics/rcd/tracks.txt
    $(CMAKE_COMMAND) -E cmake_progress_report /home/lordaro/coding/freerct.hg/CMakeFiles $(CMAKE_PROGRESS_5)
    @$(CMAKE_COMMAND) -E cmake_echo_color --switch=$(COLOR) --blue --bold "Generating rcd files from /home/lordaro/coding/freerct.hg/graphics/rcd/tracks.txt"
    cd /home/lordaro/coding/freerct.hg/graphics/rcd && ../../src/rcdgen/rcdgen /home/lordaro/coding/freerct.hg/graphics/rcd/tracks.txt

rcd: graphics/rcd/CMakeFiles/rcd
rcd: graphics/rcd/borderhighlight_8bpp64.rcd
rcd: graphics/rcd/path_8bpp64.rcd
rcd: graphics/rcd/shops.rcd
rcd: graphics/rcd/gui.rcd
rcd: graphics/rcd/tracks.rcd
....

(Note the missing targets/commands)

This causes race condition issues when run with -j2 or so
How to fix?