[yocto] libmcrypt not part of the image

[yocto yocto]

I added the meta-openembedded layer to my configuration. I want to have
libmcrypt (in meta-openembedded/meta-oe/recipes-support) on my system:

IMAGE_INSTALL += "libmcrypt"

The library (libmcrypt.so) is actually being built. Everything is located
in "libmcrypt/2.5.8-r0/package/usr", however after flashing the image
libmcrypt is not part of the filesystem.

I tried writing some kind of "libmcrypt_%.bbappend" with

do_install() {
install -m 0755 ${WORKDIR}/package/usr ${D}/
}

However, I get a bitbake error that do_install failed but there is exact
message. Any ideas how to solve this properly?
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