BUILD_STATIC flag not working

[rlorigro]

Specifying BUILD_STATIC=ON doesn't actually create static libs when using CMake:

ExternalProject_Add(project_bdsg
        GIT_REPOSITORY https://github.com/vgteam/libbdsg.git
        PREFIX ${CMAKE_SOURCE_DIR}/external/bdsg/
        CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${CMAKE_SOURCE_DIR}/external/bdsg/ -DBUILD_STATIC=ON -DRUN_DOXYGEN=OFF -DBUILD_PYTHON_BINDINGS=OFF
        BUILD_IN_SOURCE True
        INSTALL_COMMAND make install
        )

results in:

[100%] Linking CXX executable bin/test_libbdsg
/usr/bin/ld: attempted static link of dynamic object `lib/libbdsg.so'
collect2: error: ld returned 1 exit status

and a look at the lib dir shows that nothing has changed:

libbdsg.so
libdivsufsort64.so -> libdivsufsort64.so.3
libdivsufsort64.so.3 -> libdivsufsort64.so.3.0.1
libdivsufsort64.so.3.0.1
libdivsufsort.so -> libdivsufsort.so.3
libdivsufsort.so.3 -> libdivsufsort.so.3.0.1
libdivsufsort.so.3.0.1
libgtest_main.so
libgtest.so
libhandlegraph.a
libhandlegraph.so
libsdsl.so -> libsdsl.so.3
libsdsl.so.2.1.0
libsdsl.so.2.3.0
libsdsl.so.3 -> libsdsl.so.2.3.0
pkgconfig