Fix portable stat declarations for worktree detection

Signed-off-by: Nohj <vitalnohj@gmail.com>

Author: vitalNohj

src/git/git_context.c

@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 
 enum {
     GIT_CMD_MAX = 1024,