[embedded] Add an arc4random_buf stub for Linux for embedded/dependencies-random.swift test

Author: kubamracek

test/embedded/Inputs/linux-rng-support.c

@@ -0,0 +1,26 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <stdint.h>
+
+#ifdef __linux__ 
+
+ssize_t getrandom(void *buf, size_t len, unsigned int flags);
+
+void arc4random_buf(void *buf, size_t nbytes) {
+  while (nbytes > 0) {
+    ssize_t actual_nbytes = 0;
+    do {
+    	actual_nbytes = getrandom(buf, nbytes, 0);
+    } while (actual_nbytes == -1 && errno == EINTR);
+
+    if (actual_nbytes == -1) {
+      abort();
+    }
+    
+    buf = (uint8_t *)(buf) + actual_nbytes;
+    nbytes -= actual_nbytes;
+  }
+}
+
+#endif

test/embedded/dependencies-random.swift

@@ -20,7 +20,8 @@
 // DEP: _posix_memalign
 
 // RUN: %target-clang -x c -c %S/Inputs/print.c -o %t/print.o
-// RUN: %target-clang %t/a.o %t/print.o -o %t/a.out
+// RUN: %target-clang -x c -c %S/Inputs/linux-rng-support.c -o %t/linux-rng-support.o
+// RUN: %target-clang %t/a.o %t/print.o %t/linux-rng-support.o -o %t/a.out
 // RUN: %target-run %t/a.out | %FileCheck %s
 
 // REQUIRES: swift_in_compiler