gmp-4.1.4 build error "automatic de-ANSI-fication support has been removed"

porting某些package時會出現"automatic de-ANSI-fication support has been removed"，這是因為automake1.12之後，就不再支援該功能了，也就是不再支援ansi2knr這個選項了。 而且建議將AM_C_PROTOTYPES改成AC_C_PROTOTYPES的寫法，其範例如下

--- a/Makefile.am
+++ b/Makefile.am
@@ -20,7 +20,7 @@
# MA 02111-1307, USA.
-AUTOMAKE_OPTIONS = gnu no-dependencies $(top_builddir)/ansi2knr
+AUTOMAKE_OPTIONS = gnu no-dependencies

修改configure.in
--- a/configure.in
+++ b/configure.in
@@ -1501,7 +1501,9 @@ echo "      MPN_PATH=\"$path\""
# Automake ansi2knr support.
-AM_C_PROTOTYPES
+AC_C_PROTOTYPES
+AC_HEADER_STDC
+AC_CHECK_HEADERS("string.h")

參考資料：
1. https://autotools.io/forwardporting/automake.html