Build gflags from source for Travis

Summary:
Unfortunately it is not easily possible to install gflags as a package on
Travis. Change the Travis script to download and build gflags. This patch
avoids "sudo make install" so that we can continue to use Travis'
container-based infrastructure.

Test Plan: Run tests on Travis.

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D47037

.travis.yml

@@ -9,11 +9,20 @@ matrix:
       addons:
          apt:
             sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.6']
-            packages: ['clang-3.6', 'zlib1g-dev', 'libbz2-dev', 'libsnappy-dev', 'libgflags-dev']
+            packages: ['clang-3.6', 'zlib1g-dev', 'libbz2-dev', 'libsnappy-dev', 'curl']
     - os: osx
       compiler: clang
 
+install:
+  # Build gflags
+  # TODO(noetzli): Remove when gflags available through Travis
+  - pushd /tmp/ && curl -L https://github.com/gflags/gflags/archive/v2.1.2.tar.gz -o gflags.tar.gz && tar xfz gflags.tar.gz && cd gflags-2.1.2 && cmake && make && popd
+
 before_script:
+  # Add gflags to include/library paths
+  # TODO(noetzli): Remove when gflags available through Travis
+  - export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/tmp/gflags-2.1.2/lib"
+  - export CPLUS_INCLUDE_PATH="$CPLUS_INCLUDE_PATH:/tmp/gflags-2.1.2/include"
   - if [ -n "${COMPILER}" ]; then CXX=${COMPILER}; fi
   - if [[ $(uname -s) == 'Darwin' ]]; then brew install gflags snappy; fi
   - ulimit -n 2000 || true