increase RLIMIT_NOFILE locally on Linux and macOS

* closes esy#1057

bin/esy.re

@@ -2120,6 +2120,8 @@ let commandsConfig = {
 };
 
 let () = {
+  EsyLib.System.ensureMinimumFileDescriptors();
+
   let (defaultCommand, commands) = commandsConfig;
 
   /*

esy-lib/System.re

@@ -121,6 +121,9 @@ module Arch = {
 external checkLongPathRegistryKey: unit => bool =
   "esy_win32_check_long_path_regkey";
 
+external ensureMinimumFileDescriptors: unit => unit =
+  "esy_ensure_minimum_file_descriptors";
+
 let supportsLongPaths = () =>
   switch (Sys.win32) {
   | false => true

esy-lib/System.rei

@@ -46,6 +46,8 @@ module Arch: {
 
 let supportsLongPaths: unit => bool;
 
+let ensureMinimumFileDescriptors: unit => unit;
+
 module Environment: {
   /** Environment variable separator which is used for $PATH and etc */
 

esy-lib/dune

@@ -9,7 +9,7 @@
    EsyShellExpansion)
  (foreign_stubs
   (language c)
-  (names win32_path))
+  (names unix_rlimit_patch win32_path))
  (preprocess
   (pps lwt_ppx ppx_let ppx_deriving_yojson ppx_deriving.std ppx_expect
     ppx_inline_test ppx_sexp_conv)))

esy-lib/unix_rlimit_patch.c

@@ -0,0 +1,20 @@
+#include <caml/mlvalues.h>
+
+#if __APPLE__ || __linux__
+#include <sys/resource.h>
+#endif
+
+#define MIN_NOFILE 4096
+
+CAMLprim value
+esy_ensure_minimum_file_descriptors(value unit) {
+#if __APPLE__ || __linux__
+    struct rlimit limits;
+    getrlimit(RLIMIT_NOFILE, &limits);
+    if (limits.rlim_cur < MIN_NOFILE) {
+        limits.rlim_cur = MIN_NOFILE;
+        setrlimit(RLIMIT_NOFILE, &limits);
+    }
+#endif
+    return Val_unit; 
+}