Danke Guenni.
Die Pakete sind installiert, die *dev jetzt ebenfalls.
Leider bleibt trotzdem der Fehler, auf dem Pi 1B+ läuft Raspbian (stretch).
Code:
ldd ./otrpidecoder
/usr/lib/arm-linux-gnueabihf/libarmmem.so (0xb6fa7000)
libmcrypt.so.4 => /usr/lib/libmcrypt.so.4 (0xb6f56000)
libcurl.so.4 => /usr/lib/arm-linux-gnueabihf/libcurl.so.4 (0xb6eda000)
libgcc_s.so.1 => /lib/arm-linux-gnueabihf/libgcc_s.so.1 (0xb6ead000)
libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0xb6d6e000)
libnghttp2.so.14 => /usr/lib/arm-linux-gnueabihf/libnghttp2.so.14 (0xb6d40000)
libidn2.so.0 => /usr/lib/arm-linux-gnueabihf/libidn2.so.0 (0xb6d0e000)
librtmp.so.1 => /usr/lib/arm-linux-gnueabihf/librtmp.so.1 (0xb6ce5000)
libssh2.so.1 => /usr/lib/arm-linux-gnueabihf/libssh2.so.1 (0xb6cb0000)
libpsl.so.5 => /usr/lib/arm-linux-gnueabihf/libpsl.so.5 (0xb6c93000)
libssl.so.1.0.2 => /usr/lib/arm-linux-gnueabihf/libssl.so.1.0.2 (0xb6c34000)
libcrypto.so.1.0.2 => /usr/lib/arm-linux-gnueabihf/libcrypto.so.1.0.2 (0xb6ab2000)
libgssapi_krb5.so.2 => /usr/lib/arm-linux-gnueabihf/libgssapi_krb5.so.2 (0xb6a69000)
libkrb5.so.3 => /usr/lib/arm-linux-gnueabihf/libkrb5.so.3 (0xb69b2000)
libk5crypto.so.3 => /usr/lib/arm-linux-gnueabihf/libk5crypto.so.3 (0xb6973000)
libcom_err.so.2 => /lib/arm-linux-gnueabihf/libcom_err.so.2 (0xb6960000)
liblber-2.4.so.2 => /usr/lib/arm-linux-gnueabihf/liblber-2.4.so.2 (0xb6944000)
libldap_r-2.4.so.2 => /usr/lib/arm-linux-gnueabihf/libldap_r-2.4.so.2 (0xb68ef000)
libz.so.1 => /lib/arm-linux-gnueabihf/libz.so.1 (0xb68c8000)
libpthread.so.0 => /lib/arm-linux-gnueabihf/libpthread.so.0 (0xb689f000)
/lib/ld-linux-armhf.so.3 (0xb6fbd000)
libunistring.so.0 => /usr/lib/arm-linux-gnueabihf/libunistring.so.0 (0xb6790000)
libgnutls.so.30 => /usr/lib/arm-linux-gnueabihf/libgnutls.so.30 (0xb6603000)
libhogweed.so.4 => /usr/lib/arm-linux-gnueabihf/libhogweed.so.4 (0xb65c6000)
libnettle.so.6 => /usr/lib/arm-linux-gnueabihf/libnettle.so.6 (0xb657f000)
libgmp.so.10 => /usr/lib/arm-linux-gnueabihf/libgmp.so.10 (0xb650c000)
libgcrypt.so.20 => /lib/arm-linux-gnueabihf/libgcrypt.so.20 (0xb643b000)
libdl.so.2 => /lib/arm-linux-gnueabihf/libdl.so.2 (0xb6428000)
libkrb5support.so.0 => /usr/lib/arm-linux-gnueabihf/libkrb5support.so.0 (0xb640f000)
libkeyutils.so.1 => /lib/arm-linux-gnueabihf/libkeyutils.so.1 (0xb63fc000)
libresolv.so.2 => /lib/arm-linux-gnueabihf/libresolv.so.2 (0xb63d7000)
libsasl2.so.2 => /usr/lib/arm-linux-gnueabihf/libsasl2.so.2 (0xb63b0000)
libp11-kit.so.0 => /usr/lib/arm-linux-gnueabihf/libp11-kit.so.0 (0xb6352000)
libidn.so.11 => /lib/arm-linux-gnueabihf/libidn.so.11 (0xb6311000)
libtasn1.so.6 => /usr/lib/arm-linux-gnueabihf/libtasn1.so.6 (0xb62f1000)
libgpg-error.so.0 => /lib/arm-linux-gnueabihf/libgpg-error.so.0 (0xb62d1000)
libffi.so.6 => /usr/lib/arm-linux-gnueabihf/libffi.so.6 (0xb62b9000)