Do not enforce building libsqlite3 from source

Instead we now just check if it was build from source (by checking the
relevant environment variables) and if that was the case we link that
version statically.

proj-sys/Cargo.toml

@@ -12,7 +12,7 @@ links = "proj"
 rust-version = "1.70"
 
 [dependencies]
-libsqlite3-sys = { version = "0.28", features = ["bundled"] }
+libsqlite3-sys = "0.28"
 link-cplusplus = "1.0"
 
 [build-dependencies]

proj-sys/build.rs

@@ -98,14 +98,12 @@ fn build_from_source() -> Result<std::path::PathBuf, Box<dyn std::error::Error>>
     config.define("BUILD_PROJINFO", "OFF");
     config.define("BUILD_PROJSYNC", "OFF");
     config.define("ENABLE_CURL", "OFF");
-    config.define(
-        "SQLITE3_INCLUDE_DIR",
-        std::env::var("DEP_SQLITE3_INCLUDE").expect("This is set by libsqlite3-sys"),
-    );
-    config.define(
-        "SQLITE3_LIBRARY",
-        format!("{}/libsqlite3.a", std::env::var("DEP_SQLITE3_LIB_DIR").unwrap()),
-    );
+    if let Ok(sqlite_include) = std::env::var("DEP_SQLITE3_INCLUDE") {
+        config.define("SQLITE3_INCLUDE_DIR", sqlite_include);
+    }
+    if let Ok(sqlite_lib_dir) = std::env::var("DEP_SQLITE3_LIB_DIR") {
+        config.define("SQLITE3_LIBRARY", format!("{sqlite_lib_dir}/libsqlite3.a",));
+    }
 
     if cfg!(feature = "tiff") {
         eprintln!("enabling tiff support");