Move default Python selection to sanity.rs

Author: xSetech

src/bootstrap/src/core/sanity.rs

@@ -1,9 +1,10 @@
-//! Sanity checking performed by bootstrap before actually executing anything.
+//! Sanity checking and tool selection performed by bootstrap.
 //!
-//! This module contains the implementation of ensuring that the build
-//! environment looks reasonable before progressing. This will verify that
-//! various programs like git and python exist, along with ensuring that all C
-//! compilers for cross-compiling are found.
+//! This module ensures that the build environment is correctly set up before
+//! executing any build tasks. It verifies that required programs exist (like
+//! git and cmake when needed), selects appropriate tools based on the environment
+//! and platform requirements (like choosing the correct Python interpreter),
+//! and validates that C compilers for cross-compiling are available.
 //!
 //! In theory if we get past this phase it's a bug if a build fails, but in
 //! practice that's likely not true!
@@ -165,15 +166,34 @@ than building it.
         crate::exit!(1);
     }
 
-    build.config.python = build
-        .config
-        .python
-        .take()
-        .map(|p| cmd_finder.must_have(p))
-        .or_else(|| env::var_os("BOOTSTRAP_PYTHON").map(PathBuf::from)) // set by bootstrap.py
-        .or_else(|| cmd_finder.maybe_have("python"))
-        .or_else(|| cmd_finder.maybe_have("python3"))
-        .or_else(|| cmd_finder.maybe_have("python2"));
+    // Select the Python interpreter to use throughout the build.
+    //
+    // On macOS, LLDB tests require the Python version the LLDB plugin was built for.
+    // The system Python/LLDB are compatible, and many users install Homebrew Python
+    // but not Homebrew LLVM, so we default to the system Python (/usr/bin/python3).
+    // This can be overridden via the `build.python` config option for custom LLVM installations.
+    //
+    // On other platforms, we prefer the Python interpreter that invoked bootstrap.py
+    // (available via the BOOTSTRAP_PYTHON env var), then fall back to searching PATH
+    // for python, python3, or python2.
+    build.config.python = if build.host_target.ends_with("apple-darwin") {
+        build
+            .config
+            .python
+            .take()
+            .map(|p| cmd_finder.must_have(p))
+            .or_else(|| Some(PathBuf::from("/usr/bin/python3")))
+    } else {
+        build
+            .config
+            .python
+            .take()
+            .map(|p| cmd_finder.must_have(p))
+            .or_else(|| env::var_os("BOOTSTRAP_PYTHON").map(PathBuf::from)) // set by bootstrap.py
+            .or_else(|| cmd_finder.maybe_have("python"))
+            .or_else(|| cmd_finder.maybe_have("python3"))
+            .or_else(|| cmd_finder.maybe_have("python2"))
+    };
 
     build.config.nodejs = build
         .config