CI: Fix FreeBSD package installation

FreeBSD's package tool is pkg(8), and install is the command verb passed
to it.

Fixes: fb4d658 ("CI: Update Linux build scripts to use CMake p...")

.cirrus.yml

@@ -9,7 +9,7 @@ env:
 
 task:
   install_script:
-  - pkg-install -y
+  - pkg install -y
     cmake ninja binutils pkgconf curl
     ffmpeg qt6-base qt6-svg jansson libsysinfo e2fsprogs-libuuid pulseaudio
     alsa-lib pipewire v4l_compat libpci librist srt nlohmann-json uthash