message: Stipulate clang 7 in README to align with Kokoro.
diff: @@ -155,7 +155,7 @@ and tools.
  To build Filament, you must first install the following tools:
  - CMake 3.4 (or more recent)
  -- clang 5.0 (or more recent)
  +- clang 7.0 (or more recent)
  - [ninja 1.8](https://github.com/ninja-build/ninja/wiki/Pre-built-Ninja-packages) (or more recent)
  To build the Java based components of the project you can optionally install (recommended):
  @@ -231,8 +231,8 @@ If you use CMake directly instead of the build script, pass `-DENABLE_JAVA=OFF`
  Make sure you've installed the following dependencies:
  - `libglu1-mesa-dev`
  -- `libc++-dev` (`libcxx-devel` on Fedora)
  -- `libc++abi-dev`
  +- `libc++-7-dev` (`libcxx-devel` on Fedora)
  +- `libc++abi-7-dev`
  - `ninja-build`
  - `libxi-dev`
  @@ -261,8 +261,8 @@ Your Linux distribution might default to `gcc` instead of `clang`, if that's the
  ```
  $ mkdir out/cmake-release
  $ cd out/cmake-release
  -# Or use a specific version of clang, for instance /usr/bin/clang-5.0
  -$ CC=/usr/bin/clang CXX=/usr/bin/clang++ CXXFLAGS=-stdlib=libc++ \
  +# Or use a specific version of clang, for instance /usr/bin/clang-7
  +$ CC=/usr/bin/clang CXX=/usr/bin/clang++ CXXFLAGS=-stdlib=libc++ LDFLAGS=-lc++abi \
  cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=../release/filament ../..
  ```
  @@ -273,8 +273,8 @@ specific version of clang:
  ```
  $ update-alternatives --install /usr/bin/cc cc /usr/bin/clang 100
  $ update-alternatives --install /usr/bin/c++ c++ /usr/bin/clang++ 100
  -$ update-alternatives --install /usr/bin/clang clang /usr/bin/clang-5.0 100
  -$ update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-5.0 100
  +$ update-alternatives --install /usr/bin/clang clang /usr/bin/clang-7 100
  +$ update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-7 100
  ```
  Finally, invoke `ninja`:
  