I have fully compiled libcurl and inserted successfully into Leia LibreELEC distribution. This is the complete list of commands that did the trick:
cd curl
./buildconf
./configure --with-ssl --prefix=/usr
make
sudo make install
mkdir /media/pi/RASPBERRY/libreelec
cd /media/pi/RASPBERRY/libreelec
wget libreelec-rpi2.arm-8.90.003.img.gz
gunzip LibreELEC-RPi2.arm-8.90.003.img.gz
sudo losetup -o 4194304 /dev/loop0 LibreELEC-RPi2.arm-8.90.003.img
mkdir image
sudo mount /dev/loop0 image
sudo unsquashfs image/SYSTEM
sudo cp /usr/lib/libcurl.so.4.5.0 squashfs-root/usr/lib/libcurl.so.4.5.0
sudo cp /usr/bin/curl squashfs-root/usr/bin
sudo cp /usr/lib/arm-linux-gnueabihf/librtmp.so.1 squashfs-root/usr/lib/librtmp.so.1
sudo cp /usr/local/lib/libssl.so.1.1 squashfs-root/usr/lib/libssl.so.1.1
sudo cp /usr/local/lib/libcrypto.so.1.1 squashfs-root/usr/lib/libcrypto.so.1.1
sudo cp /usr/lib/arm-linux-gnueabihf/libgmp.so.10 squashfs-root/usr/lib/libgmp.so.10
sudo cp /usr/lib/arm-linux-gnueabihf/libgmp.so.10 squashfs-root/usr/lib/engines/libgmp.so.10
sudo mksquashfs squashfs-root SYSTEM -b 131072 -comp lzo -no-xattrs
md5sum SYSTEM > SYSTEM.md5
sudo mv SYSTEM* image/
sudo umount image
gzip -9 LibreELEC-RPi2.arm-8.90.003.img