ssmtp: fix to explicitely link against libcrypto

When cross-compiling following error appears at linking time, which strangely
doesn't when building "natively" within a chrooted environment.
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/bin/ld: ssmtp.o: undefined reference to symbol 'X509_free'
/bin/ld: note: 'X509_free' is defined in DSO /usr/lib/libcrypto.so.1.0.0 so try adding it to the linker command line
/usr/lib/libcrypto.so.1.0.0: could not read symbols: Invalid operation
collect2: error: ld returned 1 exit status
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musl: fixed mine to build
libprelude: fixed to build against gnutls 3.2.x
musl: add initial pieces for a musl specific shared config.cache