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

fusl/src/linux/fallocate.c

Index: fusl/src/linux/fallocate.c
diff --git a/fusl/src/linux/fallocate.c b/fusl/src/linux/fallocate.c
new file mode 100644
index 0000000000000000000000000000000000000000..ae766d5e5fa4e63a547babe811e39efb2e69e2d6
--- /dev/null
+++ b/fusl/src/linux/fallocate.c
@@ -0,0 +1,13 @@
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include "syscall.h"
+#include "libc.h"
+
+int fallocate(int fd, int mode, off_t base, off_t len)
+{
+	return syscall(SYS_fallocate, fd, mode, __SYSCALL_LL_E(base),
+		__SYSCALL_LL_E(len));
+}
+
+#undef fallocate64
+LFS64(fallocate);