sim: add support for build-time ar & ranlib

This is needed when building for a target whose ar & ranlib are
incompatible with the current build system.  For example, building
for Windows on a Linux system.

Then manually import the automake rule for libigen.a, but tweak the
tool variables to use the FOR_BUILD variants.

sim/mips/configure

@@ -697,7 +697,9 @@ RANLIB
 AR
 LDFLAGS_FOR_BUILD
 CFLAGS_FOR_BUILD
+RANLIB_FOR_BUILD
 CC_FOR_BUILD
+AR_FOR_BUILD
 INSTALL_DATA
 INSTALL_SCRIPT
 INSTALL_PROGRAM
@@ -6881,11 +6883,15 @@ $as_echo "#define AC_APPLE_UNIVERSAL_BUILD 1" >>confdefs.h
 
 
 if test "x$cross_compiling" = "xno"; then
+  : "${AR_FOR_BUILD:=\$(AR)}"
   : "${CC_FOR_BUILD:=\$(CC)}"
+  : "${RANLIB_FOR_BUILD:=\$(RANLIB)}"
   : "${CFLAGS_FOR_BUILD:=\$(CFLAGS)}"
   : "${LDFLAGS_FOR_BUILD:=\$(LDFLAGS)}"
 else
+  : "${AR_FOR_BUILD:=ar}"
   : "${CC_FOR_BUILD:=gcc}"
+  : "${RANLIB_FOR_BUILD:=ranlib}"
   : "${CFLAGS_FOR_BUILD:=-g -O}"
   : "${LDLFAGS_FOR_BUILD:=}"
 fi
@@ -6894,6 +6900,8 @@ fi
 
 
 
+
+
 if test -n "$ac_tool_prefix"; then
   # Extract the first word of "${ac_tool_prefix}ar", so it can be a program name with args.
 set dummy ${ac_tool_prefix}ar; ac_word=$2
@@ -11219,7 +11227,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11222 "configure"
+#line 11230 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11325,7 +11333,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11328 "configure"
+#line 11336 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H