musl does not implement glibc extensions such as FTW_STOP, FTW_CONTINUE, and
FTW_ACTIONRETVAL.

--- pe_profiling/operf.cpp	2017-08-08 13:44:44.573674304 -0400
+++ pe_profiling/operf.cpp	2017-08-08 13:46:27.876692262 -0400
@@ -860,9 +860,17 @@
 {
 	if (remove(fpath)) {
 		perror("sample data removal error");
+#ifdef __GLIBC__
 		return FTW_STOP;
+#else
+		return errno;
+#endif
 	} else {
+#ifdef __GLIBC__
 		return FTW_CONTINUE;
+#else
+		return 0;
+#endif
 	}
 }

@@ -897,7 +905,11 @@
 		return;

 	if (!operf_options::append) {
+#ifdef __GLIBC__
                 int flags = FTW_DEPTH | FTW_ACTIONRETVAL;
+#else
+                int flags = FTW_DEPTH;
+#endif
 		errno = 0;
 		if (nftw(previous_sampledir.c_str(), __delete_old_previous_sample_data, 32, flags) !=0 &&
 				errno != ENOENT) {
