Use execinfo.h only on glibc

libunwind could also work on musl but that would require more drastic
code changes

Github-ID: https://github.com/ibm-s390-linux/s390-tools/pull/193
Signed-off-by: Sertonix <sertonix@posteo.net>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

libutil/util_panic.c

@@ -9,12 +9,14 @@
  * it under the terms of the MIT license. See LICENSE for details.
  */
 
-#include <execinfo.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/resource.h>
 #include <sys/time.h>
+#ifdef __GLIBC__
+#include <execinfo.h>
+#endif
 
 #include "lib/util_base.h"
 #include "lib/util_panic.h"
@@ -24,6 +26,7 @@
  *
  * To get symbols, link the code with "-rdynamic".
  */
+#ifdef __GLIBC__
 static void print_backtrace(void)
 {
 	void *array[256];
@@ -42,6 +45,9 @@ static void print_backtrace(void)
 
 	free(strings);
 }
+#else
+static void print_backtrace(void) {}
+#endif
 
 /*
  * Check for core ulimit