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

fusl/src/linux/remap_file_pages.c

Index: fusl/src/linux/remap_file_pages.c
diff --git a/fusl/src/linux/remap_file_pages.c b/fusl/src/linux/remap_file_pages.c
new file mode 100644
index 0000000000000000000000000000000000000000..a9699ce2e4f7d71c18cf500bacbfda4c47e86ce2
--- /dev/null
+++ b/fusl/src/linux/remap_file_pages.c
@@ -0,0 +1,8 @@
+#define _GNU_SOURCE
+#include <sys/mman.h>
+#include "syscall.h"
+
+int remap_file_pages(void *addr, size_t size, int prot, size_t pgoff, int flags)
+{
+	return syscall(SYS_remap_file_pages, addr, size, prot, pgoff, flags);
+}