gitlab-ci: Run Autotools tests with out-of-tree (VPATH) builds

.gitlab-ci/test.sh

@@ -8,5 +8,7 @@
 make -j$(nproc)
 cd ..
 
-sh autogen.sh $CONFIG --with-libxml-src=libxml2
+mkdir -p libxslt-build
+cd libxslt-build
+sh ../autogen.sh $CONFIG --with-libxml-src=../libxml2
 make -j$(nproc) V=1 CFLAGS="$CFLAGS -Werror"
@@ -12,2 +14,2 @@
 make -j$(nproc) V=1 CFLAGS="$CFLAGS -Werror"
-make -s check
+make -s CFLAGS="$CFLAGS -Werror" check