How to satisfy 'libadwaita-1' build dependency (in gnome/meson)?

You are trying to make Ubuntu act as Gentoo, LFS or ArchLinux. So you did wrong steps.

To build/rebuild/patch gnome-calculator you have to get its sources for deb-package for your Ubuntu 21.10 release. At first enable Source Code repositories from Software & Updates (software-properties-gtk) and then execute the following commands:

sudo apt-get install build-essential dpkg-dev devscripts
sudo apt-get build-dep gnome-calculator

cd ~/Downloads
apt-get source gnome-calculator
cd gnome-calculator-40.1/
# do some patching/coding here
dpkg-buildpackage -uc -us

sudo apt-get install ../gnome-calculator_40.1-1ubuntu2_amd64.deb

If you are sure about compilation of latest non-Ubuntu gnome-calculator version - then you have to build libadwaita-1 package from upcoming 22.04 LTS first by:

sudo apt-get install debhelper-compat dh-sequence-gir libgirepository1.0-dev libgnome-desktop-3-dev libgtk-4-dev meson sassc valac xvfb

cd ~/Downloads
wget http://archive.ubuntu.com/ubuntu/pool/universe/liba/libadwaita-1/libadwaita-1_1.0.0~alpha.2.orig.tar.gz
cd libadwaita-1-1.0.0~alpha.2/
wget http://archive.ubuntu.com/ubuntu/pool/universe/liba/libadwaita-1/libadwaita-1_1.0.0~alpha.2-1.debian.tar.xz
tar -xf libadwaita-1_1.0.0~alpha.2-1.debian.tar.xz
rm libadwaita-1_1.0.0~alpha.2-1.debian.tar.xz

export DEB_BUILD_OPTIONS=nocheck
dpkg-buildpackage -uc -us
sudo apt-get install ../*adw*.deb

and then proceed with compilation of missed libgtksourceview-5-dev package:

sudo apt-get install dh-sequence-gnome gtk-doc-tools libxml2-utils libglib2.0-doc libgtk-3-doc libgdk-pixbuf2.0-doc libpango1.0-doc

cd ~/Downloads
wget http://archive.ubuntu.com/ubuntu/pool/universe/g/gtksourceview5/gtksourceview5_5.2.0.orig.tar.xz
cd gtksourceview-5.2.0/
wget http://archive.ubuntu.com/ubuntu/pool/universe/g/gtksourceview5/gtksourceview5_5.2.0-2.debian.tar.xz
tar -xf gtksourceview5_5.2.0-2.debian.tar.xz
rm gtksourceview5_5.2.0-2.debian.tar.xz
dpkg-buildpackage -uc -us
sudo apt-get install ../*gtksource*.deb

And only then you can try to proceed with compilation of git master-branch version of gnome-calculator.