Add test/cmake_subdir_test

.travis.yml

@@ -1,4 +1,4 @@
-# Copyright 2016, 2017 Peter Dimov
+# Copyright 2016-2019 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
 
@@ -250,6 +250,15 @@ matrix:
       compiler: clang++
       env: TOOLSET=clang COMPILER=clang++ CXXSTD=03,11,14,1z
 
+    - os: linux
+      compiler: g++
+      env: CMAKE_SUBDIR_TEST=1
+      script:
+      - cd test/cmake_subdir_test && mkdir __build__ && cd __build__
+      - cmake ..
+      - cmake --build .
+      - cmake --build . --target check
+
 install:
   - BOOST_BRANCH=develop && [ "$TRAVIS_BRANCH" == "master" ] && BOOST_BRANCH=master || true
   - cd ..