add use-vendored-config feature

lvgl-sys/Cargo.toml

@@ -22,3 +22,6 @@ cty = "0.2.1"
 [build-dependencies]
 cc = "1.0.68"
 bindgen = "0.59.2"
+
+[features]
+use-vendored-config = []

lvgl-sys/build.rs

@@ -19,10 +19,16 @@ fn main() {
                         // so let's use the vendored `lv_conf.h` file.
                         vendor.join("include")
                     }
-                    Err(_) => panic!(
+                    Err(_) => {
+                        #[cfg(not(feature = "use-vendored-config"))]
+                        panic!(
                             "The environment variable {} is required to be defined",
                             CONFIG_NAME
-                    ),
+                        );
+
+                        #[cfg(feature = "use-vendored-config")]
+                        vendor.join("include")
+                    }
                 }
             });
 

lvgl/Cargo.toml

@@ -21,6 +21,7 @@ bitflags = "1.2.1"
 [features]
 alloc = ["cstr_core/alloc"]
 lvgl_alloc = ["alloc"]
+use-vendored-config = ["lvgl-sys/use-vendored-config"]
 
 [build-dependencies]
 quote = "1.0.9"