[m-rev.] trivial diff: fix typo in configure script

[Julien Fischer]

Branches: 14.01, master

Fix a typo in the configure script.

configure.ac:
 	Add a missing '=' character in a variable assignment.

Julien.

diff --git a/configure.ac b/configure.ac
index dede274..034ced5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4674,7 +4674,7 @@ case "$mercury_cv_cc_type" in
          CFLAGS_FOR_OPT=
          # XXX See README.MS-Visual C for details of why we disable this.
          #CFLAGS_FOR_DEBUG="-Zi"
-        CFLAGS_FOR_DEBUG
+        CFLAGS_FOR_DEBUG=
          CFLAGS_FOR_NO_STRICT_ALIASING=

          # Using the MSVC compiler implies that we must use