Write yosys version to output files

kernel/driver.cc

@@ -31,9 +31,6 @@
 #include "kernel/register.h"
 #include "kernel/log.h"
 
-// from kernel/version_*.o (cc source generated from Makefile)
-extern const char *yosys_version_str;
-
 bool fgetline(FILE *f, std::string &buffer)
 {
 	buffer = "";

kernel/register.h

@@ -31,6 +31,9 @@
 extern Tcl_Interp *yosys_get_tcl_interp();
 #endif
 
+// from kernel/version_*.o (cc source generated from Makefile)
+extern const char *yosys_version_str;
+
 // implemented in driver.cc
 extern RTLIL::Design *yosys_get_design();
 std::string rewrite_yosys_exe(std::string exe);