Below you is my build instructions for GnuPG 2.1.20 released on 03-Apr-2017. These instructions are built for a headless Ubuntu 16.04 LTS server.
Or if you wish, you may use the install script to install GnuPG 2.1.20 by entring the following:
curl -sL "https://gist.github.com/mattrude/3883a3801613b048d45b/raw/install-gnupg2.sh" |sh
apt-get -y install libgnutls-dev bzip2 make gettext texinfo gnutls-bin \
build-essential g++
mkdir -p /var/src/gnupg21 && cd /var/src/gnupg21
gpg --list-keys
gpg --recv-keys 0x4F25E3B6 0xE0856959 0x33BD3F06 0x7EFD60D9 0xF7E48EDB
wget -c ftp://ftp.gnupg.org/gcrypt/libgpg-error/libgpg-error-1.27.tar.gz && \
wget -c ftp://ftp.gnupg.org/gcrypt/libgpg-error/libgpg-error-1.27.tar.gz.sig && \
gpg --verify libgpg-error-1.27.tar.gz.sig && tar -xzf libgpg-error-1.27.tar.gz && \
cd libgpg-error-1.27/ && ./configure && make && make install && cd ../
wget -c ftp://ftp.gnupg.org/gcrypt/libgcrypt/libgcrypt-1.7.6.tar.gz && \
wget -c ftp://ftp.gnupg.org/gcrypt/libgcrypt/libgcrypt-1.7.6.tar.gz.sig && \
gpg --verify libgcrypt-1.7.6.tar.gz.sig && tar -xzf libgcrypt-1.7.6.tar.gz && \
cd libgcrypt-1.7.6 && ./configure && make && make install && cd ../
wget -c ftp://ftp.gnupg.org/gcrypt/libassuan/libassuan-2.4.3.tar.bz2 && \
wget -c ftp://ftp.gnupg.org/gcrypt/libassuan/libassuan-2.4.3.tar.bz2.sig && \
gpg --verify libassuan-2.4.3.tar.bz2.sig && tar -xjf libassuan-2.4.3.tar.bz2 && \
cd libassuan-2.4.3 && ./configure && make && make install && cd ../
wget -c ftp://ftp.gnupg.org/gcrypt/libksba/libksba-1.3.5.tar.bz2 && \
wget -c ftp://ftp.gnupg.org/gcrypt/libksba/libksba-1.3.5.tar.bz2.sig && \
gpg --verify libksba-1.3.5.tar.bz2.sig && tar -xjf libksba-1.3.5.tar.bz2 && \
cd libksba-1.3.5 && ./configure && make && make install && cd ../
wget -c ftp://ftp.gnupg.org/gcrypt/npth/npth-1.3.tar.bz2 && \
wget -c ftp://ftp.gnupg.org/gcrypt/npth/npth-1.3.tar.bz2.sig && \
gpg --verify npth-1.3.tar.bz2.sig && tar -xjf npth-1.3.tar.bz2 && \
cd npth-1.3 && ./configure && make && make install && cd ../
wget -c ftp://ftp.gnu.org/gnu/ncurses/ncurses-6.0.tar.gz && \
wget -c ftp://ftp.gnu.org/gnu/ncurses/ncurses-6.0.tar.gz.sig && \
gpg --verify ncurses-6.0.tar.gz.sig && tar -xzf ncurses-6.0.tar.gz && \
cd ncurses-6.0 && export CPPFLAGS="-P" && ./configure && make && make install && cd ../
wget -c ftp://ftp.gnupg.org/gcrypt/pinentry/pinentry-1.0.0.tar.bz2 && \
wget -c ftp://ftp.gnupg.org/gcrypt/pinentry/pinentry-1.0.0.tar.bz2.sig && \
gpg --verify pinentry-1.0.0.tar.bz2.sig && tar -xjf pinentry-1.0.0.tar.bz2 && \
cd pinentry-1.0.0 && ./configure --enable-pinentry-curses --disable-pinentry-qt4 && \
make && make install && cd ../
wget -c ftp://ftp.gnupg.org/gcrypt/gnupg/gnupg-2.1.20.tar.bz2 && \
wget -c ftp://ftp.gnupg.org/gcrypt/gnupg/gnupg-2.1.20.tar.bz2.sig && \
gpg --verify gnupg-2.1.20.tar.bz2.sig && tar -xjf gnupg-2.1.20.tar.bz2 && \
cd gnupg-2.1.20 && ./configure && make && make install && echo $?
echo "/usr/local/lib" > /etc/ld.so.conf.d/gpg2.conf && ldconfig -v
There is also an update for pinentry.
ftp://ftp.gnupg.org/gcrypt/pinentry/pinentry-0.9.7.tar.bz2
But, I'm not sure if updating to it is a good idea. Can't remember exactly, but I have a faint memory of newer versions not working as well. Don't quote me on that, though, and please, do test.
Also, someone forked this script to include those two updated versions.
https://gist.github.com/vt0r/a2f8c0bcb1400131ff51