Depend on libsqlite3-sys for bundled builds (#190)

This commit adds an optional dependency to libsqlite3-sys to provide a
bundled version of libsqlite3 as well instead of relying on a system
provided version.

---------

Co-authored-by: Michael Kirk <michael.code@endoftheworl.de>

proj-sys/Cargo.toml

@@ -12,6 +12,8 @@ links = "proj"
 rust-version = "1.70"
 
 [dependencies]
+libsqlite3-sys = "0.28"
+link-cplusplus = "1.0"
 
 [build-dependencies]
 bindgen = "0.68.1"

proj-sys/build.rs

@@ -72,6 +72,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 // returns the path of "include" for the built proj
 fn build_from_source() -> Result<std::path::PathBuf, Box<dyn std::error::Error>> {
     eprintln!("building libproj from source");
+    println!("cargo:rustc-cfg=bundled_build");
     if let Ok(val) = &env::var("_PROJ_SYS_TEST_EXPECT_BUILD_FROM_SRC") {
         if val == "0" {
             panic!(
@@ -80,7 +81,6 @@ fn build_from_source() -> Result<std::path::PathBuf, Box<dyn std::error::Error>>
         }
     }
 
-    // NOTE: The PROJ build expects Sqlite3 to be present on the system.
     let path = "PROJSRC/proj-9.4.0.tar.gz";
     let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
     let tar_gz = File::open(path)?;
@@ -99,6 +99,20 @@ fn build_from_source() -> Result<std::path::PathBuf, Box<dyn std::error::Error>>
     config.define("BUILD_PROJSYNC", "OFF");
     config.define("ENABLE_CURL", "OFF");
 
+    // we check here whether or not these variables are set by cargo
+    // if they are set, `libsqlite3-sys` was built with the bundled feature
+    // enabled, which in turn allows us to rely on the built libsqlite3 version
+    // and link it statically
+    //
+    // If these are not set, it's necessary that libsqlite3 exists on the build system
+    // in a location accessible by cmake
+    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");
         config.define("ENABLE_TIFF", "ON");
@@ -132,9 +146,6 @@ fn build_from_source() -> Result<std::path::PathBuf, Box<dyn std::error::Error>>
         &out_path.join("build/lib").display()
     );
 
-    // The PROJ library needs SQLite and the C++ standard library.
-    println!("cargo:rustc-link-lib=dylib=sqlite3");
-
     if cfg!(feature = "tiff") {
         // On platforms like apples aarch64, users are likely to have installed libtiff with homebrew,
         // which isn't in the default search path, so try to determine path from pkg-config
@@ -159,13 +170,5 @@ fn build_from_source() -> Result<std::path::PathBuf, Box<dyn std::error::Error>>
         println!("cargo:rustc-link-lib=dylib=tiff");
     }
 
-    if cfg!(target_os = "linux") {
-        println!("cargo:rustc-link-lib=dylib=stdc++");
-    } else if cfg!(target_os = "macos") {
-        println!("cargo:rustc-link-lib=dylib=c++");
-    } else {
-        println!("cargo:warning=proj-sys: Not configuring an explicit C++ standard library on this target.");
-    }
-
     Ok(proj.join("include"))
 }

proj-sys/src/lib.rs

@@ -28,6 +28,11 @@
 //! implement your own set of callbacks if you wish to make use of them (see the
 //! [`proj`](https://crates.io/crates/proj) crate for an example).
 
+#[cfg(bundled_build)]
+extern crate libsqlite3_sys;
+#[cfg(bundled_build)]
+extern crate link_cplusplus;
+
 #[cfg(not(feature = "nobuild"))]
 include!(concat!(env!("OUT_DIR"), "/bindings.rs"));