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

fusl/src/misc/setrlimit.c

+#include <sys/resource.h>
+#include <errno.h>
+#include "syscall.h"
+#include "libc.h"
+
+#define MIN(a, b) ((a)<(b) ? (a) : (b))
+#define FIX(x) do{ if ((x)>=SYSCALL_RLIM_INFINITY) (x)=RLIM_INFINITY; }while(0)
+
+int __setrlimit(int resource, const struct rlimit *rlim)
+{
+        unsigned long k_rlim[2];
+        struct rlimit tmp;
+        if (SYSCALL_RLIM_INFINITY != RLIM_INFINITY) {
+                tmp = *rlim;
+                FIX(tmp.rlim_cur);
+                FIX(tmp.rlim_max);
+                rlim = &tmp;
+        }
+        int ret = __syscall(SYS_prlimit64, 0, resource, rlim, 0);
+        if (ret != -ENOSYS) return ret;
+        k_rlim[0] = MIN(rlim->rlim_cur, MIN(-1UL, SYSCALL_RLIM_INFINITY));
+        k_rlim[1] = MIN(rlim->rlim_max, MIN(-1UL, SYSCALL_RLIM_INFINITY));
+        return __syscall(SYS_setrlimit, resource, k_rlim);
+}
+
+struct ctx {
+        const struct rlimit *rlim;
+        int res;
+        int err;
+};
+
+static void do_setrlimit(void *p)
+{
+        struct ctx *c = p;
+        if (c->err>0) return;
+        c->err = -__setrlimit(c->res, c->rlim);
+}
+
+int setrlimit(int resource, const struct rlimit *rlim)
+{
+        struct ctx c = { .res = resource, .rlim = rlim, .err = -1 };
+        __synccall(do_setrlimit, &c);
+        if (c.err) {
+                if (c.err>0) errno = c.err;
+                return -1;
+        }
+        return 0;
+}
+
+LFS64(setrlimit);