tools/alpine: Add iucode_tool to base

The iucode_tool is used to convert the Intel CPU microcode
binaries into a cpio archive. There is no alpine package
for it, so compile it from source.

This is for x86_64 only and on other archs we create a empty
file.

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

tools/alpine/iucode-tool.patch

@@ -0,0 +1,12 @@
+diff --git a/iucode_tool.c b/iucode_tool.c
+index 460087c..8825ed6 100644
+--- a/iucode_tool.c
++++ b/iucode_tool.c
+@@ -31,6 +31,7 @@
+ #include <dirent.h>
+ #include <time.h>
+ #include <cpuid.h>
++#include <limits.h>
+ 
+ #include "intel_microcode.h"
+