addr2line.c: fix r60841 for glibc before 2.22

SHF_COMPRESSED was not defined until glibc 2.22, and there are
older distros (e.g. Debian 8.x jessie) which do not have this
defined.

Perhaps it is safe to define SHF_COMPRESSED to (1 << 11) ourselves,
too, since ELF should be a standardized format.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60843 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

addr2line.c

@@ -95,6 +95,10 @@ void *alloca();
 #define PATH_MAX 4096
 #endif
 
+#ifndef SHF_COMPRESSED /* compatibility with glibc < 2.22 */
+#define SHF_COMPRESSED 0
+#endif
+
 int kprintf(const char *fmt, ...);
 
 typedef struct {