[m-rev.] diff: Link with -lm when checking for fma function.

[Peter Wang]

configure.ac:
    As above.
---
 configure.ac | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 148dafc41..3d827e8e8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1382,11 +1382,17 @@ mercury_check_for_functions \
         access sleep opendir readdir closedir mkdir symlink readlink \
         gettimeofday setenv putenv _putenv posix_spawn sched_setaffinity \
         sched_getaffinity sched_getcpu sched_yield mkstemp mkdtemp \
-        setrlimit fma getcontext dl_iterate_phdr
+        setrlimit getcontext dl_iterate_phdr
 
 mercury_check_for_stdio_functions \
         snprintf _snprintf vsnprintf _vsnprintf
 
+save_LIBS="$LIBS"
+LIBS="$MATH_LIB"
+mercury_check_for_functions \
+        fma
+LIBS="$save_LIBS"
+
 #-----------------------------------------------------------------------------#
 
 MERCURY_CHECK_FOR_HEADERS( \
-- 
2.16.2