.travis.yml: add cmake support

Simplify PKG_CONFIG_PATH and LDFLAGS while at it using the new
--enable-asan option which automatically adds the required flags if
available. LDFLAGS is ignored by cmake, but apparently cmake builds
packages with the correct rpath without any further options.

Additionally, build examples by default (without -Werror) and remove
"cat config.log" which would result in configure succeeding while it
should not.

.travis.yml

 dist: trusty
+env:
+  matrix:
+    - CI_BUILD=cmake
+    - CI_BUILD=autotools
 language: cpp
 os:
 #  - osx
@@ -35,9 +39,11 @@ before_script:
   - ./ci/build_openssl.sh
   - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew install libev; fi
   # configure ngtcp2
-  - autoreconf -i
-  - if [ "$TRAVIS_OS_NAME" == "linux" ]; then ./configure --enable-werror PKG_CONFIG_PATH=$PWD/../openssl/build/lib/pkgconfig CPPFLAGS=-fsanitize=address LDFLAGS="$EXTRA_LDFLAGS -fsanitize=address -Wl,-rpath,$PWD/openssl/build/lib" || cat config.log; fi
-  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then ./configure --enable-werror PKG_CONFIG_PATH=$PWD/../openssl/build/lib/pkgconfig LDFLAGS="-Wl,-rpath,$PWD/openssl/build/lib"; fi
+  - if [ "$CI_BUILD" == "autotools" ]; then autoreconf -i; fi
+  - export PKG_CONFIG_PATH=$PWD/../openssl/build/lib/pkgconfig LDFLAGS="$EXTRA_LDFLAGS -Wl,-rpath,$PWD/openssl/build/lib"
+  - if [ "$CI_BUILD" == "autotools" ]; then ./configure --enable-werror --enable-asan; fi
+  - if [ "$CI_BUILD" == "cmake" ]; then cmake -DENABLE_ASAN=1; fi
 script:
-  # Now build ngtcp2
+  # Now build ngtcp2 examples and test
+  - make
   - make check