wget -c http://ftp.mozilla.org/pub/mozilla.org/nspr/releases/v4.19/src/nspr-4.19.tar.gz
tar -xzf nspr-4.19.tar.gz
cd nspr-4.19
mkdir -p build
cd build
../nspr/configure --prefix="/usr" --enable-64bit # don't force 32bit
make # Doesn't mind -j#
make install