Revert r103230, which depended on ld preserving the __start_xxx and

__stop_xxx symbols for custom sections, even when these were not
referenced (at link time).  This behaviour was changed again in binutils
commit 0b8ed435c3fe8bd09a08c23920e65bfb03251221.

This time, put the __GLOBL macro definition in cdefs.h, so it can be
reused in a few other places where it will be needed.

Reviewed by:	kib

sys/sys/cdefs.h

@@ -401,6 +401,9 @@
 #endif	/* __STDC__ */
 #endif	/* __GNUC__ || __INTEL_COMPILER */
 
+#define	__GLOBL1(sym)	__asm__(".globl " #sym)
+#define	__GLOBL(sym)	__GLOBL1(sym)
+
 #if defined(__GNUC__) || defined(__INTEL_COMPILER)
 #define	__IDSTRING(name,string)	__asm__(".ident\t\"" string "\"")
 #else

sys/sys/linker_set.h

@@ -45,6 +45,8 @@
  */
 #ifdef __GNUCLIKE___SECTION
 #define __MAKE_SET(set, sym)						\
+	__GLOBL(__CONCAT(__start_set_,set));				\
+	__GLOBL(__CONCAT(__stop_set_,set));				\
 	static void const * const __set_##set##_sym_##sym 		\
 	__section("set_" #set) __used = &sym
 #else /* !__GNUCLIKE___SECTION */