use docker

.travis.yml

@@ -44,11 +44,8 @@ matrix:
       os: osx
     - env: TARGET=i586-unknown-linux-gnu
       os: linux
-      dist: trusty
-      addons:
-        apt:
-          packages:
-            - gcc-multilib
+      services: docker
+      sudo: required
     - env: TARGET=i686-unknown-linux-gnu
       os: linux
       addons:

ci/env.sh

@@ -30,10 +30,15 @@ case $TARGET in
         export PREFIX=arm-linux-gnueabihf-
         export QEMU_LD_PREFIX=/usr/arm-linux-gnueabihf
         ;;
+    i586-unknown-linux-gnu)
+        # NOTE $DOCKER values: 'y' (yes, call docker), 'i' (inside a docker container) or 'n' ("no)
+        if [[ -z $DOCKER ]]; then
+            export DOCKER=y
+        fi
+        ;;
     mips-unknown-linux-gnu)
         # See #2
         export DONT_RUN_TESTS=y
-        # NOTE $DOCKER values: 'y' (yes, call docker), 'i' (inside a docker container) or 'n' ("no)
         if [[ -z $DOCKER ]]; then
             export DOCKER=y
         fi

ci/install.sh

@@ -38,6 +38,10 @@ install_c_toolchain() {
             sudo apt-get install -y --no-install-recommends \
                  gcc-aarch64-linux-gnu libc6-dev-arm64-cross
             ;;
+        i586-unknown-linux-gnu)
+            apt-get install -y --no-install-recommends \
+                    gcc libc6-dev-i386
+            ;;
         mips-unknown-linux-gnu)
             apt-get install -y --no-install-recommends \
                     gcc-mips-linux-gnu libc6-dev-mips-cross