ci: Run tests on i386 cross builds

Yes, some tests fail, but we can turn those into XFAILs at meson time.
Better to keep the things that work working than not cover them at all.
Unfortunately XPASS results will not cause the build to fail until we
update CI to meson 0.51 or newer.

Reviewed-by: Daniel Stone <daniels@collabora.com>

.gitlab-ci/cross-xfail-i386

@@ -0,0 +1 @@
+u_format_test

.gitlab-ci/meson-build.sh

@@ -14,9 +14,32 @@ else
     touch native.file
 fi
 
+CROSS_FILE=/cross_file-"$CROSS".txt
+
+# cross-xfail-$CROSS, if it exists, contains a list of tests that are expected
+# to fail for the $CROSS configuration, one per line. you can then mark those
+# tests in their meson.build with:
+#
+# test(...,
+#      should_fail: meson.get_cross_property('xfail', '').contains(t),
+#     )
+#
+# where t is the name of the test, and the '' is the string to search when
+# not cross-compiling (which is empty, because for amd64 everything is
+# expected to pass).
+if [ -n "$CROSS" ]; then
+    CROSS_XFAIL=.gitlab-ci/cross-xfail-"$CROSS"
+    if [ -s "$CROSS_XFAIL" ]; then
+        sed -i \
+            -e '/\[properties\]/a\' \
+            -e "xfail = '$(tr '\n' , < $CROSS_XFAIL)'" \
+            "$CROSS_FILE"
+    fi
+fi
+
 rm -rf _build
 meson _build --native-file=native.file \
-      ${CROSS+--cross /cross_file-$CROSS.txt} \
+      ${CROSS+--cross "$CROSS_FILE"} \
       -D prefix=`pwd`/install \
       -D libdir=lib \
       -D buildtype=${BUILDTYPE:-debug} \
@@ -45,7 +68,7 @@ rm -rf install/include
 
 # Strip the drivers in the artifacts to cut 80% of the artifacts size.
 if [ -n "$CROSS" ]; then
-    STRIP=`sed -n -E "s/strip\s*=\s*'(.*)'/\1/p" /cross_file-$CROSS.txt`
+    STRIP=`sed -n -E "s/strip\s*=\s*'(.*)'/\1/p" "$CROSS_FILE"`
     if [ -z "$STRIP" ]; then
         echo "Failed to find strip command in cross file"
         exit 1