When compiling ET_2020_05, I obtained linking errors against LAPACK and BLAS even though these were set to BUILD in the optionslist.

After further review, the issue turned out to be that bindings/Configuration/Capabilities/make.BLAS.defn and make.LAPACK.defn both had the libraries listed in LAPACK_DIR/lib and BLAS_DIR/lib respectively, however, the configure.sh scripts for both libs copies the static library to LAPACK_DIR and BLAS_DIR respectively. For instance:
ExternalLibraries/LAPACK/configure.sh

        echo "LAPACK: Installing..."
        cp liblapack.a ${LAPACK_DIR}
        popd

Changing the LAPACK_LIB_DIRS and BLAS_LIB_DIRS to the base directory where the library is located results in correct linking.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2464/linking-errors-with-et_2020_05-with-etk