fmf: Use mkosi -f together with ToolsTreePackageDirectories=

There's no need to build various systemd tools from source again to
build the mkosi image when we can just install the packages that were
already built from source into the tools tree so let's do that to avoid
unnecessary compiling.

test/fmf/integration-tests/test.sh

@@ -57,6 +57,7 @@ SELinuxRelabel=yes
 [Build]
 ToolsTreeDistribution=${MKOSI_DISTRIBUTION:-$ID}
 ToolsTreeRelease=${MKOSI_RELEASE:-${VERSION_ID:-rawhide}}
+ToolsTreePackageDirectories=..
 Environment=NO_BUILD=1
 WithTests=yes
 EOF
@@ -90,7 +91,7 @@ mkosi summary
 mkosi -f sandbox -- true
 mkosi sandbox -- meson setup --buildtype=debugoptimized -Dintegration-tests=true build
 mkosi genkey
-mkosi sandbox -- meson compile -C build mkosi
+mkosi -f
 mkosi sandbox -- \
     meson test \
     -C build \