Ninja build on Arch failing with HAVE_COLORD, HAVE_PACKAGEKIT not found

I'm trying to build simple-scan git:master according to the README instructions. Meson correctly finds all dependencies. However, when ninja tries to compile, it fails, saying that colord and packagekit are missing (see below).

There was an earlier, similar bug relating the autotools vs. meson. It looks like that issue was resolved in version 25. Assuming master is newer than v25, I think this is different from my problem.
https://bugs.launchpad.net/simple-scan/+bug/1462769

Meson/Ninja/Vala are all new to me, and simple-scan is targeted for a different distro than I'm using, so this is very likely user/configuration error on my part. Any pointers on what's failing here, why it's failing, and how to get around it?

Many thanks!

$ ninja all install
[1/14] Compiling Vala source ../src/config.vapi ../src/app-window.vala ../src/authorize-dialog.vala ../s...g.vala ../src/simple-scan.vala ../src/scanner.vala ../src/screensaver.vala ../src/autosave-manager.vala.
FAILED: src/simple-scan@exe/app-window.c src/simple-scan@exe/authorize-dialog.c src/simple-scan@exe/book.c src/simple-scan@exe/book-view.c src/simple-scan@exe/page.c src/simple-scan@exe/page-view.c src/simple-scan@exe/preferences-dialog.c src/simple-scan@exe/simple-scan.c src/simple-scan@exe/scanner.c src/simple-scan@exe/screensaver.c src/simple-scan@exe/autosave-manager.c
valac -C --debug --pkg libwebpmux --pkg libwebp --pkg packagekit-glib2 --pkg colord --pkg sane-backends --pkg gusb --pkg gdk-pixbuf-2.0 --pkg cairo --pkg zlib --pkg gtk+-3.0 --target-glib ' 2.38' --pkg glib-2.0 -d src/simple-scan@exe --gresources=../src/simple-scan.gresource.xml --pkg=posix --vapidir=/home/dan/Projects/simple-scan/src HAVE_COLORD HAVE_PACKAGEKIT -D HAVE_WEBP ../src/config.vapi ../src/app-window.vala ../src/authorize-dialog.vala ../src/book.vala ../src/book-view.vala ../src/page.vala ../src/page-view.vala ../src/preferences-dialog.vala ../src/simple-scan.vala ../src/scanner.vala ../src/screensaver.vala ../src/autosave-manager.vala
error: HAVE_COLORD not found
error: HAVE_PACKAGEKIT not found
Compilation failed: 2 error(s), 0 warning(s)
ninja: build stopped: subcommand failed.