In musl libc there is no execinfo.h and no backtrace()

--- cegui/src/Exceptions.cpp	2014-07-07 09:06:18.000000000 +0200
+++ cegui/src/Exceptions.cpp	2015-08-02 17:29:59.057854926 +0200
@@ -37,7 +37,7 @@
 
 #if defined(_MSC_VER)
 #include <dbghelp.h>
-#elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__HAIKU__)
+#elif (defined(__linux__) && defined(__GLIBC__)) || defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__HAIKU__)
 #include <execinfo.h>
 #include <dlfcn.h>
 #include <cxxabi.h>
@@ -129,7 +129,7 @@
     logger.logEvent("==========  End of Backtrace  ==========", Errors);
 
     SymCleanup(GetCurrentProcess());
-#elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__HAIKU__)
+#elif (defined(__linux__) && defined(__GLIBC__)) || defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__HAIKU__)
     void* buffer[frames];
     const int received = backtrace(&buffer[0], frames);