configure: Use AC_COMPILE_IFELSE for ICU check for cross compilation compat

AC_RUN_IFELSE doesn't work when cross compiling, but we can do the
check in the preprocessor instead, so use AC_COMPILE_IFELSE instead.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
---
 configure.ac |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: beecrypt-4.2.1/configure.ac
===================================================================
--- beecrypt-4.2.1.orig/configure.ac
+++ beecrypt-4.2.1/configure.ac
@@ -295,13 +295,13 @@
 if test "$ac_with_cplusplus" = yes; then
   AC_MSG_CHECKING([for IBM's ICU library version >= 2.8])
   AC_LANG_PUSH(C)
-  AC_RUN_IFELSE([
+  AC_COMPILE_IFELSE([
     AC_LANG_PROGRAM([[#include <unicode/uversion.h>]],[[
       #if U_ICU_VERSION_MAJOR_NUM < 2
-      exit(1);
+      #error too old
       #elif U_ICU_VERSION_MAJOR_NUM == 2
       # if U_ICU_VERSION_MINOR_NUM < 8
-      exit(1);
+      #error too old
       # else
       exit(0);
       # endif