Switch to "meson setup"

Fixes this warning:

    WARNING: Running the setup command as `meson [options]` instead of `meson setup [options]` is ambiguous and deprecated.

.builds/alpine.yml

@@ -13,8 +13,8 @@ artifacts:
 tasks:
   - setup: |
       cd libliftoff
-      CC=gcc meson build-gcc/ --fatal-meson-warnings -Db_coverage=true
+      CC=gcc meson setup build-gcc/ --fatal-meson-warnings -Db_coverage=true
-      CC=clang meson build-clang/ --fatal-meson-warnings -Db_sanitize=address,undefined -Db_lundef=false
+      CC=clang meson setup build-clang/ --fatal-meson-warnings -Db_sanitize=address,undefined -Db_lundef=false
   - build-gcc: |
       cd libliftoff
       ninja -C build-gcc/

.builds/freebsd.yml

@@ -8,7 +8,7 @@ sources:
 tasks:
 - setup: |
     cd libliftoff
-    meson build/ --fatal-meson-warnings
+    meson setup build/ --fatal-meson-warnings
 - build: |
     cd libliftoff
     ninja -C build/

README.md

@@ -20,7 +20,7 @@ is underway to integrate it with [wlroots].
 
 Depends on libdrm. Requires universal planes and atomic.
 
-    meson build/
+    meson setup build/
     ninja -C build/
 
 ## Usage