Diagnose clang failures

.travis.yml

@@ -13,7 +13,7 @@ env:
 
 script:
   - cmake -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DFMT_EXTRA_TESTS=ON .
-  - make -j4
+  - make -j4 VERBOSE=1
   - CTEST_OUTPUT_ON_FAILURE=1 make test
 
 after_failure:

CMakeLists.txt

@@ -66,6 +66,7 @@ if (WIN32)
 else ()
   check_symbol_exists(open fcntl.h HAVE_OPEN)
 endif ()
+message("HAVE_OPEN: ${HAVE_OPEN}")
 if (HAVE_OPEN)
   add_definitions(-DFMT_USE_FILE_DESCRIPTORS=1)
   set(FMT_SOURCES ${FMT_SOURCES} posix.cc posix.h)