travis: use ninja-build for CMake builds

Added package ninja-build to environment
Use ninja to speed up CMake builds

Closes #6077

scripts/travis/before_script.sh

@@ -71,21 +71,16 @@ if [ "$TRAVIS_OS_NAME" = linux -a "$BORINGSSL" ]; then
   cd $HOME
   git clone --depth=1 https://boringssl.googlesource.com/boringssl
   cd boringssl
-  mkdir build
-  cd build
-  CXX="g++" CC="gcc" cmake -DCMAKE_BUILD_TYPE=release -DBUILD_SHARED_LIBS=1 ..
-  make
-  cd ..
+  CXX="g++" CC="gcc" cmake -H. -Bbuild -GNinja -DCMAKE_BUILD_TYPE=release -DBUILD_SHARED_LIBS=1
+  cmake --build build
   mkdir lib
-  cd lib
-  cp ../build/crypto/libcrypto.so .
-  cp ../build/ssl/libssl.so .
-  echo "BoringSSL lib dir: "`pwd`
-  cd ../build
-  make clean
-  rm -f CMakeCache.txt
-  CXX="g++" CC="gcc" cmake -DCMAKE_POSITION_INDEPENDENT_CODE=on ..
-  make
+  cp ./build/crypto/libcrypto.so ./lib/
+  cp ./build/ssl/libssl.so ./lib/
+  echo "BoringSSL lib dir: "`pwd`"/lib"
+  cmake --build build --target clean
+  rm -f build/CMakeCache.txt
+  CXX="g++" CC="gcc" cmake -H. -Bbuild -GNinja -DCMAKE_POSITION_INDEPENDENT_CODE=on
+  cmake --build build
   export LIBS=-lpthread
 fi