Use gnustep package rather than compiling it.

.travis.yml

@@ -18,14 +18,8 @@ matrix:
       env: FEATURES="exception" IOS_ARCHS="i386 x86_64 armv7 armv7s aarch64"
 sudo: false
 install: ./travis_install.sh
-before_script: >
-  if [ "$TRAVIS_OS_NAME" = "linux" ]; then
-    export LIBRARY_PATH=$HOME/libobjc2_staging/lib:$LIBRARY_PATH;
-    export LD_LIBRARY_PATH=$HOME/libobjc2_staging/lib:$LD_LIBRARY_PATH;
-  fi
 script: ./travis_test.sh
 addons:
   apt:
     packages:
-      - clang
-      - cmake
+      - gnustep-devel

travis_install.sh

@@ -9,16 +9,6 @@ rust_ios_install() {
     "./${ios_stdlib}/install.sh" --prefix=$(rustc --print sysroot)
 }
 
-gnustep_install() {
-    git clone https://github.com/gnustep/libobjc2.git
-    mkdir libobjc2/build
-    cd libobjc2/build
-    export CC="clang"
-    export CXX="clang++"
-    cmake -DCMAKE_INSTALL_PREFIX:PATH=$HOME/libobjc2_staging ../
-    make install
-}
-
 for arch in $IOS_ARCHS; do
     rust_ios_install "$arch"
 done
@@ -27,7 +17,3 @@ if [ -n "$IOS_ARCHS" ]; then
     curl -LO https://github.com/SSheldon/rust-test-ios/releases/download/0.1.1/rust-test-ios
     chmod +x rust-test-ios
 fi
-
-if [ "$TRAVIS_OS_NAME" = "linux" ]; then
-    gnustep_install
-fi