configure.ac: fix reading of HLINT environment variable

configure.ac advertised that the HLINT environment variable could be set to
specify the path to the 'hlint' tool. However, HLINT was being initialized
to "no" inside configure.ac, which broke this usage.

Signed-off-by: Dato Simó <dato@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

configure.ac

@@ -629,7 +629,6 @@ fi
 AC_SUBST(HTOOLS_APIDOC)
 
 # Check for hlint
-HLINT=no
 AC_ARG_VAR(HLINT, [hlint path])
 AC_PATH_PROG(HLINT, [hlint], [])
 if test -z "$HLINT"; then