enable Travis to do -m32

Author: Daniel Kroening

.travis.yml

@@ -83,6 +83,7 @@ jobs:
             - g++-5
             - libubsan0
             - parallel
+            - libc6-dev-i386
       before_install:
         - mkdir bin ; ln -s /usr/bin/gcc-5 bin/gcc
       # env: COMPILER=g++-5 SAN_FLAGS="-fsanitize=undefined -fno-sanitize-recover -fno-omit-frame-pointer"
@@ -115,6 +116,7 @@ jobs:
             - libwww-perl
             - g++-5
             - libubsan0
+            - libc6-dev-i386
       before_install:
         - mkdir bin ; ln -s /usr/bin/gcc-5 bin/gcc
       # env: COMPILER=g++-5 SAN_FLAGS="-fsanitize=undefined -fno-sanitize-recover -fno-omit-frame-pointer"
@@ -140,6 +142,7 @@ jobs:
             - libstdc++-5-dev
             - libubsan0
             - parallel
+            - libc6-dev-i386
       before_install:
         - mkdir bin ; ln -s /usr/bin/clang-3.7 bin/gcc
         - export CCACHE_CPP2=yes
@@ -165,6 +168,7 @@ jobs:
             - clang-3.7
             - libstdc++-5-dev
             - libubsan0
+            - libc6-dev-i386
       before_install:
         - mkdir bin ; ln -s /usr/bin/clang-3.7 bin/gcc
         - export CCACHE_CPP2=yes