travis: Add clover build using llvm-3.9

Use r600,radeonsi instead of i915
Update binutils, new linker is required for llvm-3.9:
https://www.ubuntuupdates.org/package/core/trusty/universe/updates/binutils-2.26

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>

.travis.yml

@@ -151,6 +151,45 @@ matrix:
             - libx11-xcb-dev
             - libelf-dev
             - libunwind8-dev
+    - env:
+        # NOTE: Analogous to SWR above, building Clover is quite slow.
+        - LABEL="make Gallium ST Clover LLVM-3.9"
+        - BUILD=make
+        - MAKEFLAGS="-j4"
+        - MAKE_CHECK_COMMAND="true"
+        - LLVM_VERSION=3.9
+        - LLVM_CONFIG="llvm-config-${LLVM_VERSION}"
+        - OVERRIDE_CC=gcc-4.7
+        - OVERRIDE_CXX=g++-4.7
+        # New binutils linker is required for llvm-3.9
+        - OVERRIDE_PATH=/usr/lib/binutils-2.26/bin
+        - DRI_LOADERS="--disable-glx --disable-gbm --disable-egl"
+        - DRI_DRIVERS=""
+        - GALLIUM_ST="--disable-dri --enable-opencl --enable-opencl-icd --enable-llvm --disable-xa --disable-nine --disable-xvmc --disable-vdpau --disable-va --disable-omx-bellagio --disable-gallium-osmesa"
+        - GALLIUM_DRIVERS="r600,radeonsi"
+        - VULKAN_DRIVERS=""
+        - LIBUNWIND_FLAGS="--enable-libunwind"
+      addons:
+        apt:
+          sources:
+            - llvm-toolchain-trusty-3.9
+          packages:
+            - binutils-2.26
+            - libclc-dev
+            # LLVM packaging is broken and misses these dependencies
+            - libedit-dev
+            - g++-4.7
+            # From sources above
+            - llvm-3.9-dev
+            - clang-3.9
+            - libclang-3.9-dev
+            # Common
+            - xz-utils
+            - x11proto-xf86vidmode-dev
+            - libexpat1-dev
+            - libx11-xcb-dev
+            - libelf-dev
+            - libunwind8-dev
     - env:
         - LABEL="make Gallium ST Other"
         - BUILD=make
@@ -378,6 +417,8 @@ script:
   - if test "x$BUILD" = xmake; then
       test -n "$OVERRIDE_CC" && export CC="$OVERRIDE_CC";
       test -n "$OVERRIDE_CXX" && export CXX="$OVERRIDE_CXX";
+      test -n "$OVERRIDE_PATH" && export PATH="$OVERRIDE_PATH:$PATH";
+
       export CC="$CC -isystem`pwd`";
 
       ./autogen.sh --enable-debug