build: remove AX_GCC_FUNC_ATTRIBUTE test for dllimport

The result of this test isn't currently used anywhere (we use dllimport based on
MSC_VER in libconsensus).

Author: fanquake

configure.ac

@@ -813,8 +813,6 @@ if test x$ac_cv_sys_large_files != x &&
   CPPFLAGS="$CPPFLAGS -D_LARGE_FILES=$ac_cv_sys_large_files"
 fi
 
-AX_GCC_FUNC_ATTRIBUTE([dllimport])
-
 if test x$use_glibc_compat != xno; then
   AX_CHECK_LINK_FLAG([[-Wl,--wrap=__divmoddi4]], [COMPAT_LDFLAGS="$COMPAT_LDFLAGS -Wl,--wrap=__divmoddi4"])
   AX_CHECK_LINK_FLAG([[-Wl,--wrap=log2f]], [COMPAT_LDFLAGS="$COMPAT_LDFLAGS -Wl,--wrap=log2f"])