configure.ac: checking that OpenMP is not supported directly by the c…

…ompiler before searching for separate preprocessor and library to enable it.

configure.ac

@@ -35,12 +35,13 @@ AC_CONFIG_SUBDIRS([src/smithlab_cpp])
 
 dnl OpenMP happens here
 AC_OPENMP([C++])
+AS_VAR_IF(OPENMP_CXXFLAGS, [], [
 dnl check for the OpenMP library; can't be later
 AC_SEARCH_LIBS([omp_get_num_threads], [gomp omp], [],
                [AC_MSG_FAILURE([OpenMP library not found])])
 dnl now we get setup for the right OpenMP flags
 ADS_OPENMP([], [AC_MSG_FAILURE([OpenMP must be installed to build abismal])])
-dnl end of OpenMP stuff
+])dnl end of OpenMP stuff
 
 dnl check for the Zlib library
 AC_CHECK_LIB([z], [zlibVersion], [],