Apple-darwin: set DEBUG_LTO_BUILD_DOESNT_WORK for

Temporary workaround for the well known
"the undefined references problem for debug-assertions+lto" (rust-lang#79)

Author: paoloteti

.travis.yml

@@ -13,6 +13,7 @@ matrix:
     - env: TARGET=i586-unknown-linux-gnu
     - env: TARGET=i686-apple-darwin
       os: osx
+      env: DEBUG_LTO_BUILD_DOESNT_WORK=1
     - env: TARGET=i686-unknown-linux-gnu
     - env: TARGET=mips-unknown-linux-gnu
     - env: TARGET=mips64-unknown-linux-gnuabi64
@@ -30,6 +31,7 @@ matrix:
       script: cargo build --target $TARGET
     - env: TARGET=x86_64-apple-darwin
       os: osx
+      env: DEBUG_LTO_BUILD_DOESNT_WORK=1
     - env: TARGET=x86_64-unknown-linux-gnu
   allow_failures:
     - env: TARGET=thumbv6m-linux-eabi