improve machinery for ldso to report libc version

eliminate gratuitous glue function for reporting the version, which
was probably leftover from the old dynamic linker design which lacked
a clear barrier for when/how it could access global data. put the
declaration for the data object that replaces it in libc.h where it
can be type checked.

ldso/dynlink.c

@@ -99,8 +99,6 @@ int __init_tp(void *);
 void __init_libc(char **, char *);
 void *__copy_tls(unsigned char *);
 
-hidden const char *__libc_get_version(void);
-
 static struct builtin_tls {
 	char c;
 	struct pthread pt;
@@ -1562,7 +1560,7 @@ _Noreturn void __dls3(size_t *sp)
 				"Version %s\n"
 				"Dynamic Program Loader\n"
 				"Usage: %s [options] [--] pathname%s\n",
-				__libc_get_version(), ldname,
+				__libc_version, ldname,
 				ldd_mode ? "" : " [args]");
 			_exit(1);
 		}

src/internal/libc.h

@@ -43,6 +43,8 @@ extern hidden size_t __hwcap;
 extern hidden size_t __sysinfo;
 extern char *__progname, *__progname_full;
 
+extern hidden const char __libc_version[];
+
 /* Designed to avoid any overhead in non-threaded processes */
 hidden void __lock(volatile int *);
 hidden void __unlock(volatile int *);

src/internal/version.c

 #include "version.h"
 #include "libc.h"
 
-static const char version[] = VERSION;
-
-hidden const char *__libc_get_version()
-{
-	return version;
-}
+const char __libc_version[] = VERSION;