docs: Document MSVC ABI environment support

Update the crate level docstrings and README file.

Author: ravenexp

README.md

@@ -2,18 +2,23 @@ Standalone `python3.dll` import library generator
 =================================================
 
 Generates import libraries for the Stable ABI Python DLL
-for MinGW-w64 cross-compile targets.
+for MinGW-w64 and MSVC (cross-)compile targets.
 
 See <https://docs.python.org/3/c-api/stable.html> for details.
 
 This crate **does not require** Python 3 distribution files
-to be present on the cross-compile host system.
+to be present on the (cross-)compile host system.
+
+**Note:** MSVC (cross-)compile targets require LLVM binutils
+to be available on the host system.
+More specifically, `python3-dll-a` requires `llvm-dlltool` executable
+to be present in `PATH` when targeting `*-pc-windows-msvc`.
 
 Example `build.rs` script
 -------------------------
 
 The following script can be used to cross-compile Stable ABI
-PyO3 extension modules for Windows:
+PyO3 extension modules for Windows (64-bit MinGW-w64):
 
 ```rust
 fn main() {
@@ -29,18 +34,19 @@ fn main() {
 A compatible `python3.dll` import library will be automatically created in
 the directory pointed by `PYO3_CROSS_LIB_DIR` environment variable.
 
-If both 64-bit and 32-bit Windows cross-compile targets support is needed,
-the more generic `generate_implib_for_target()` function must be used:
+If both 64-bit and 32-bit or GNU and MSVC ABI (cross-)compile target
+support is needed, the more generic `generate_implib_for_target()`
+function must be used:
+
 
 ```rust
 fn main() {
-    if std::env::var("CARGO_CFG_TARGET_OS").unwrap() == "windows"
-        && std::env::var("CARGO_CFG_TARGET_ENV").unwrap() == "gnu"
-    {
+    if std::env::var("CARGO_CFG_TARGET_OS").unwrap() == "windows" {
         let libdir = std::env::var("PYO3_CROSS_LIB_DIR")
             .expect("PYO3_CROSS_LIB_DIR is not set when cross-compiling");
         let arch = std::env::var("CARGO_CFG_TARGET_ARCH").unwrap();
-        python3_dll_a::generate_implib_for_target(&libdir, &arch, "gnu")
+        let env = std::env::var("CARGO_CFG_TARGET_ENV").unwrap();
+        python3_dll_a::generate_implib_for_target(&libdir, &arch, &env)
             .expect("python3.dll import library generator failed");
     }
 }

src/lib.rs

@@ -2,18 +2,23 @@
 //! =================================================
 //!
 //! Generates import libraries for the Stable ABI Python DLL
-//! for MinGW-w64 cross-compile targets.
+//! for MinGW-w64 and MSVC (cross-)compile targets.
 //!
 //! See <https://docs.python.org/3/c-api/stable.html> for details.
 //!
 //! This crate **does not require** Python 3 distribution files
-//! to be present on the cross-compile host system.
+//! to be present on the (cross-)compile host system.
+//!
+//! **Note:** MSVC (cross-)compile targets require LLVM binutils
+//! to be available on the host system.
+//! More specifically, `python3-dll-a` requires `llvm-dlltool` executable
+//! to be present in `PATH` when targeting `*-pc-windows-msvc`.
 //!
 //! Example `build.rs` script
 //! -------------------------
 //!
 //! The following script can be used to cross-compile Stable ABI
-//! PyO3 extension modules for Windows (64-bit):
+//! PyO3 extension modules for Windows (64-bit MinGW-w64):
 //!
 //! ```no_run
 //! fn main() {
@@ -29,18 +34,18 @@
 //! A compatible `python3.dll` import library will be automatically created in
 //! the directory pointed by `PYO3_CROSS_LIB_DIR` environment variable.
 //!
-//! If both 64-bit and 32-bit Windows cross-compile targets support is needed,
-//! the more generic `generate_implib_for_target()` function must be used:
+//! If both 64-bit and 32-bit or GNU and MSVC ABI (cross-)compile target
+//! support is needed, the more generic `generate_implib_for_target()`
+//! function must be used:
 //!
 //! ```no_run
 //! fn main() {
-//!     if std::env::var("CARGO_CFG_TARGET_OS").unwrap() == "windows"
-//!         && std::env::var("CARGO_CFG_TARGET_ENV").unwrap() == "gnu"
-//!     {
+//!     if std::env::var("CARGO_CFG_TARGET_OS").unwrap() == "windows" {
 //!         let libdir = std::env::var("PYO3_CROSS_LIB_DIR")
 //!             .expect("PYO3_CROSS_LIB_DIR is not set when cross-compiling");
 //!         let arch = std::env::var("CARGO_CFG_TARGET_ARCH").unwrap();
-//!         python3_dll_a::generate_implib_for_target(&libdir, &arch, "gnu")
+//!         let env = std::env::var("CARGO_CFG_TARGET_ENV").unwrap();
+//!         python3_dll_a::generate_implib_for_target(&libdir, &arch, &env)
 //!             .expect("python3.dll import library generator failed");
 //!     }
 //! }