In order to be able to build OpenJDK for Linux/ia64 (Zero variant), the autoconf platform definitions need to be added to platform.m4.

This is trivially achieved by:

diff -r 3a5291f51ba2 make/autoconf/platform.m4
--- a/make/autoconf/platform.m4 Fri Mar 23 23:57:48 2018 +0000
+++ b/make/autoconf/platform.m4 Sun Mar 25 13:05:31 2018 +0200
@@ -60,6 +60,12 @@
       VAR_CPU_BITS=64
       VAR_CPU_ENDIAN=little
       ;;
+ ia64)
+ VAR_CPU=ia64
+ VAR_CPU_ARCH=ia64
+ VAR_CPU_BITS=64
+ VAR_CPU_ENDIAN=little
+ ;;
     m68k)
       VAR_CPU=m68k
       VAR_CPU_ARCH=m68k