Add a "fork" of musl as //fusl.

fusl/src/stdio/perror.c

Index: fusl/src/stdio/perror.c
diff --git a/fusl/src/stdio/perror.c b/fusl/src/stdio/perror.c
new file mode 100644
index 0000000000000000000000000000000000000000..fdcb4d71c8855201c8a67858e8fa607fff038744
--- /dev/null
+++ b/fusl/src/stdio/perror.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include "stdio_impl.h"
+
+void perror(const char *msg)
+{
+	FILE *f = stderr;
+	char *errstr = strerror(errno);
+
+	FLOCK(f);
+	
+	if (msg && *msg) {
+		fwrite(msg, strlen(msg), 1, f);
+		fputc(':', f);
+		fputc(' ', f);
+	}
+	fwrite(errstr, strlen(errstr), 1, f);
+	fputc('\n', f);
+
+	FUNLOCK(f);
+}