configure: break long line.

configure.ac

@@ -308,7 +308,8 @@ AC_DEFINE_UNQUOTED([HAVE_DECL___LZCNT64],
 dnl
 AC_CACHE_CHECK([whether __builtin_complex is available],
   [acx_cv_have_decl___builtin_complex],
-  [AC_LINK_IFELSE([AC_LANG_PROGRAM([@%:@include <complex.h>],[   long double _Complex c =  __builtin_complex(1.0L, -2.5L)])],
+  [AC_LINK_IFELSE([AC_LANG_PROGRAM([@%:@include <complex.h>],
+       [   long double _Complex c =  __builtin_complex(1.0L, -2.5L)])],
      [AS_VAR_SET([acx_cv_have_decl___builtin_complex],[yes])],
      [AS_VAR_SET([acx_cv_have_decl___builtin_complex],[no])])])
 ACX_CHECK_ASM_BSR