Expand symlinks in default configuration paths for iOS devices

CFSearchPathForDirectoriesInDomains returns a path in /var, while
getenv(HOME) returns the same path in /private/var. /var is a symlink
to /private/var, but when config is generated, the difference in paths
means they won't be abbreviated correctly.

This change expands symlinks before filling in the default
directories, so those paths will match.

frontend/drivers/platform_darwin.m

@@ -48,6 +48,7 @@
 
 #include <boolean.h>
 #include <compat/apple_compat.h>
+#include <retro_assert.h>
 #include <retro_miscellaneous.h>
 #include <file/file_path.h>
 #include <rhash.h>
@@ -335,6 +336,15 @@ static void frontend_darwin_get_environment_settings(int *argc, char *argv[],
    CFSearchPathForDirectoriesInDomains(CFDocumentDirectory,
          CFUserDomainMask, 1, home_dir_buf, sizeof(home_dir_buf));
 
+#if TARGET_OS_IPHONE
+   char resolved_home_dir_buf[PATH_MAX_LENGTH] = {0};
+   if (realpath(home_dir_buf, resolved_home_dir_buf)) {
+      retro_assert(strlcpy(home_dir_buf,
+            resolved_home_dir_buf,
+            sizeof(home_dir_buf)) < sizeof(home_dir_buf));
+   }
+#endif
+
    strlcat(home_dir_buf, "/RetroArch", sizeof(home_dir_buf));
    fill_pathname_join(g_defaults.dirs[DEFAULT_DIR_SHADER],
          home_dir_buf, "shaders_glsl",