Add Mac implementation of oc_run_cmd

so much easier than windows, oh my goodness

src/orca.c

@@ -29,6 +29,7 @@
     #include "platform/posix_io.c"
     #include "platform/posix_thread.c"
     #include "platform/osx_platform.c"
+    #include "platform/osx_subprocess.c"
 
 /*
 	#include"platform/unix_rng.c"

src/platform/osx_subprocess.c

@@ -0,0 +1,60 @@
+/*************************************************************************
+*
+*  Orca
+*  Copyright 2023 Martin Fouilleul and the Orca project contributors
+*  See LICENSE.txt for licensing information
+*
+**************************************************************************/
+#include "platform_subprocess.h"
+
+#include <stdio.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+oc_str8 oc_run_cmd(oc_arena* arena, oc_str8 cmd)
+{
+    const char* cmdC = oc_str8_to_cstring(arena, cmd);
+    FILE* p = popen(cmdC, "r+");
+    if(!p)
+    {
+        oc_log_error("failed to launch process");
+        return OC_STR8("");
+    }
+
+    oc_str8_list chunks = { 0 };
+    char buffer[1024];
+    while(true)
+    {
+        ssize_t nRead = read(fileno(p), buffer, sizeof(buffer));
+        if(nRead < 0)
+        {
+            oc_log_error("failed to read from process's stdout\n");
+            return OC_STR8("");
+        }
+        if(nRead == 0)
+        {
+            break;
+        }
+
+        oc_str8 chunk = oc_str8_from_buffer(nRead, buffer);
+        oc_str8_list_push(arena, &chunks, oc_str8_push_copy(arena, chunk));
+    }
+
+    int status = pclose(p);
+    if(status == -1)
+    {
+        oc_log_warning("failed to close subprocess\n");
+    }
+    else if(!WIFEXITED(status))
+    {
+        oc_log_warning("subprocess did not exit correctly\n");
+    }
+
+    return oc_str8_list_join(arena, chunks);
+}
+
+#ifdef __cplusplus
+} // extern "C"
+#endif