As proposed by @jirson-tavera in the homebrew-php repo issue, this can be fixed without overriding your brew installation:
wget -c http://www.ijg.org/files/jpegsrc.v8d.tar.gz
tar xzf jpegsrc.v8d.tar.gz
cd jpeg-8d
./configure
make
cp ./.libs/libjpeg.8.dylib /usr/local/opt/jpeg/lib