Allow cross compilation prefix to come from CROSS_COMPILE environment variable

Configure

@@ -1047,6 +1047,8 @@ $default_ranlib= &which("ranlib") or $default_ranlib="true";
 $perl=$ENV{'PERL'} or $perl=&which("perl5") or $perl=&which("perl")
   or $perl="perl";
 
+$cross_compile_prefix=$ENV{'CROSS_COMPILE'};
+
 chop $openssldir if $openssldir =~ /\/$/;
 chop $prefix if $prefix =~ /.\/$/;