build: add doxygen.dox to distribution
build: add doxygen.dox to distribution

Without this file, the doxygen documentation cannot be generated,
causing build failures with distribution tarballs. On the other hand,
adding the autogenerated man pages to the distribution is unnecessary,
they will deleted and regenerated anyway.

Signed-off-by: Jonas Witschel <87a164e5d00d5dcdd001e37b34ea8bcd3fc3a172@gmx.de>

01org/tpm2-tss,01org/TPM2.0-TSS,01org/tpm2-tss,tpm2-software/tpm2-tss,01org/tpm2-tss,tpm2-software/tpm2-tss,01org/TPM2.0-TSS,tpm2-software/tpm2-tss,01org/TPM2.0-TSS,01org/TPM2.0-TSS