.travis.yml: added ubuntu-toolchain-r-test for asan32
diff --git a/.travis.yml b/.travis.yml
index cb5bc0e..4e47ab1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -47,6 +47,8 @@
       env: PLATFORM="Ubuntu 12.04" CMD="make asan32"
       addons:
         apt:
+          sources:
+            - ubuntu-toolchain-r-test
           packages:
             - libc6-dev-i386
             - gcc-multilib