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

fusl/src/stat/fchmodat.c

Index: fusl/src/stat/fchmodat.c
diff --git a/fusl/src/stat/fchmodat.c b/fusl/src/stat/fchmodat.c
new file mode 100644
index 0000000000000000000000000000000000000000..d94667aed5e1a4aa1e924bd89a8ba3aa3ec6aa16
--- /dev/null
+++ b/fusl/src/stat/fchmodat.c
@@ -0,0 +1,39 @@
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include "syscall.h"
+
+void __procfdname(char *, unsigned);
+
+int fchmodat(int fd, const char *path, mode_t mode, int flag)
+{
+	if (!flag) return syscall(SYS_fchmodat, fd, path, mode, flag);
+
+	if (flag != AT_SYMLINK_NOFOLLOW)
+		return __syscall_ret(-EINVAL);
+
+	struct stat st;
+	int ret, fd2;
+	char proc[15+3*sizeof(int)];
+
+	if ((ret = __syscall(SYS_fstatat, fd, path, &st, flag)))
+		return __syscall_ret(ret);
+	if (S_ISLNK(st.st_mode))
+		return __syscall_ret(-EOPNOTSUPP);
+
+	if ((fd2 = __syscall(SYS_openat, fd, path, O_RDONLY|O_PATH|O_NOFOLLOW|O_NOCTTY|O_CLOEXEC)) < 0) {
+		if (fd2 == -ELOOP)
+			return __syscall_ret(-EOPNOTSUPP);
+		return __syscall_ret(fd2);
+	}
+
+	__procfdname(proc, fd2);
+	ret = __syscall(SYS_fstatat, AT_FDCWD, proc, &st, 0);
+	if (!ret) {
+		if (S_ISLNK(st.st_mode)) ret = -EOPNOTSUPP;
+		else ret = __syscall(SYS_fchmodat, AT_FDCWD, proc, mode);
+	}
+
+	__syscall(SYS_close, fd2);
+	return __syscall_ret(ret);
+}