Add a build using ARM to Cirrus CI

Use matrix to perform the same build steps for different platforms and
account for FreeBSD specific things by explicitly checking the OS name
in the scripts.

.cirrus.yml

@@ -9,9 +9,18 @@ env:
 
 task:
   skip: "changesIncludeOnly('appveyor.yml','CMakeLists.txt','.github/**','docs/**','interface/**','include/wx/{msw,osx,qt}/**','src/{msw,osx,qt}/**','build/{cmake,msw,osx}/**')"
-  name: Cirrus CI / FreeBSD 13 wxGTK 3
-  freebsd_instance:
-    image_family: freebsd-13-0
+  matrix:
+    - name: Cirrus CI / FreeBSD 13 wxGTK 3
+      freebsd_instance:
+        image_family: freebsd-13-0
+      env:
+        osname: FreeBSD
+    - name: Cirrus CI / Debian ARM wxGTK 3
+      arm_container:
+        image: debian:11-slim
+      env:
+        osname: Linux
+        arch: arm
 
   before_script: |
     echo LD_LIBRARY_PATH=`pwd`/lib >> $CIRRUS_ENV
@@ -34,17 +43,24 @@ task:
 
   # Rather than getting all submodules, get just the ones we need, as we can
   # use system libraries instead of the other ones.
-  update_submodues_script: |
+  update_submodules_script: |
     git submodule update --init 3rdparty/catch 3rdparty/nanosvg
 
   ccache_cache:
     folder: /tmp/ccache
 
-  # We need to pass flags so that libraries under /usr/local are found, because
-  # configure doesn't look for them there by default (it ought to always use
-  # pkg-config instead, but it currently doesn't do this either).
   configure_script: |
-    ./configure --disable-optimise --disable-debug_info CXXFLAGS=-Werror CPPFLAGS=-I/usr/local/include LDFLAGS=-L/usr/local/lib
+    case "${osname}" in
+      FreeBSD)
+        # We need to pass these flags so that libraries under /usr/local are found,
+        # because configure doesn't look for them there by default (it ought to
+        # always use pkg-config instead, but it currently doesn't do this either).
+        CPPFLAGS=-I/usr/local/include
+        LDFLAGS=-L/usr/local/lib
+        ;;
+    esac
+
+    ./configure --disable-optimise --disable-debug_info CXXFLAGS=-Werror CPPFLAGS=$CPPFLAGS LDFLAGS=$LDFLAGS
 
   build_library_script: |
     make -k $wxBUILD_ARGS
@@ -59,10 +75,15 @@ task:
   build_samples_script: |
     make -k -C samples $wxBUILD_ARGS
 
-  # Building sample requires GNU make, so install it just for this.
   install_script: |
     make install
-    pkg install -q -y gmake
+    case "${osname}" in
+      FreeBSD)
+        # Building sample requires GNU make, so install it just for this.
+        pkg install -q -y gmake
+        ;;
+    esac
+
     gmake -C samples/minimal -f makefile.unx clean
     gmake -C samples/minimal -f makefile.unx $wxBUILD_ARGS