feat: Add ImportLibraryGenerator::abiflags() method

Allow specifying the generated import library ABI flags as well
as the interpreter version.

Only `"t"` is currently supported as the ABI flags parameter value
and only for CPython v3.13.

Author: ravenexp

src/lib.rs

@@ -175,6 +175,11 @@ pub struct ImportLibraryGenerator {
     version: Option<(u8, u8)>,
     /// Python interpreter implementation
     implementation: PythonImplementation,
+    /// Optional Python ABI flags
+    ///
+    /// For example, `"t"` stands for the free-threaded CPython v3.13 build
+    /// aka CPython `3.13t`.
+    abiflags: Option<String>,
 }
 
 impl ImportLibraryGenerator {
@@ -186,11 +191,12 @@ impl ImportLibraryGenerator {
     /// The compile target environment ABI name (as in `CARGO_CFG_TARGET_ENV`)
     /// is passed in `env`.
     pub fn new(arch: &str, env: &str) -> Self {
-        Self {
+        ImportLibraryGenerator {
             arch: arch.to_string(),
             env: env.to_string(),
             version: None,
             implementation: PythonImplementation::CPython,
+            abiflags: None,
         }
     }
 
@@ -202,6 +208,19 @@ impl ImportLibraryGenerator {
         self
     }
 
+    /// Sets the ABI flags for the `pythonXY<abi>.dll` import library.
+    ///
+    /// For example, `"t"` stands for the free-threaded CPython v3.13 build
+    /// aka CPython `3.13t`.
+    /// In this case, `python313t.dll` import library will be generated.
+    ///
+    /// The untagged versioned `pythonXY.dll` import library
+    /// is generated by default.
+    pub fn abiflags(&mut self, flags: Option<&str>) -> &mut Self {
+        self.abiflags = flags.map(ToOwned::to_owned);
+        self
+    }
+
     /// Sets Python interpreter implementation
     pub fn implementation(&mut self, implementation: PythonImplementation) -> &mut Self {
         self.implementation = implementation;
@@ -256,7 +275,11 @@ impl ImportLibraryGenerator {
                 Some((3, 10)) => ("python310.def", include_str!("python310.def")),
                 Some((3, 11)) => ("python311.def", include_str!("python311.def")),
                 Some((3, 12)) => ("python312.def", include_str!("python312.def")),
-                Some((3, 13)) => ("python313.def", include_str!("python313.def")),
+                Some((3, 13)) => match self.abiflags.as_deref() {
+                    Some("t") => ("python313t.def", include_str!("python313t.def")),
+                    None => ("python313.def", include_str!("python313.def")),
+                    _ => return Err(Error::new(ErrorKind::Other, "Unsupported Python ABI flags")),
+                },
                 _ => return Err(Error::new(ErrorKind::Other, "Unsupported Python version")),
             },
             PythonImplementation::PyPy => match self.version {