--- a/simgear/misc/strutils.cxx	2020-06-26 00:07:33.000000000 +0200
+++ b/simgear/misc/strutils.cxx	2020-08-22 19:50:07.043076612 +0200
@@ -1169,7 +1175,13 @@
   // Always makes the string in 'buf' null-terminated
   retcode = strerror_s(buf, sizeof(buf), errnum);
 #elif defined(_GNU_SOURCE)
+#if defined(__GLIBC__)
   return std::string(strerror_r(errnum, buf, sizeof(buf)));
+#else
+  int retcode;
+  // Musl libc support
+  retcode = strerror_r(errnum, buf, sizeof(buf));
+#endif
 #elif (_POSIX_C_SOURCE >= 200112L) || defined(SG_MAC) || defined(__FreeBSD__) || defined(__OpenBSD__)
   int retcode;
   // POSIX.1-2001 and POSIX.1-2008
@@ -1178,7 +1184,7 @@
 #error "Could not find a thread-safe alternative to strerror()."
 #endif
 
-#if !defined(_GNU_SOURCE)
+#if !defined(_GNU_SOURCE) || !defined(__GLIBC__)
   if (retcode) {
     std::string msg = "unable to get error message for a given error number";
     // C++11 would make this shorter with std::to_string()