Feature: Add command execution on child processes feature

Temporary: Add configuration sample for forward compatibility

src/command.c

@@ -0,0 +1,60 @@
+#include "command.h"
+
+#include "memory.h"
+#include "discovery.h"
+#include "io.h"
+#include "utils.h"
+#include "config.h"
+
+#include <assert.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+// TODO: This file is UNSAFE. This file is purely here for MVP purposes, and to self-host this program itself.
+
+Command command_create(Arena* a, Discovery* d, Configuration* c)
+{
+  assert(d != NULL);
+  assert(a != NULL);
+  assert(c != NULL);
+  
+  Command cmd;
+  cmd.a = a;
+  cmd.app = d->cc;
+
+  size_t args_len = d->c_count + 2;
+  const char** args_buf = (const char**)arena_alloc(a, sizeof(const char*) * (args_len));
+  args_buf[0] = d->cc.buf;
+
+  for(size_t i = 0; i < d->c_count; i++)
+  {
+    args_buf[i+1] = d->c_files[i]->path.buf;
+    LOG_DEBUG("File to build: %s", d->c_files[i]->path);
+  }
+
+  args_buf[args_len - 1] = NULL;
+  cmd.args = args_buf;
+  return cmd;
+}
+
+int command_run(Command* cmd)
+{
+  assert(cmd != NULL);
+  if(cmd->args == NULL) DIE("No arguments were supplied to the command");
+
+  pid_t pid = fork();
+
+  if(pid == -1) DIE("fork failed, could not create child process.");
+  
+  if(pid == 0)
+  {
+    if(execvp(cmd->app.buf, (char*const*)cmd->args) == -1)
+      DIE("Failed to launch command: %s.", cmd->app.buf);
+  }
+
+  int wstatus = 0;
+  if(waitpid(pid, &wstatus, 0) == -1) DIE("wait failed.");
+  LOG_DEBUG("Command calling app %s exited with status code %d on child process PID %d.", cmd->app.buf, wstatus, pid);
+  return wstatus;
+}
+