arrow: Fix cross-compiling errors on macos

This fixes the issue with missing LZ4 symbols in the arm64
wheel first introduced in v3.1.1.

The crux of the issue is that Arrow was building lz4 (and zstd) in a
separate cmake build, and it does not specially pass on the
`CMAKE_OSX_ARCHITECTURES` flag that was set when perspective-server's
build script invokes cmake.

Arrow's build does forward on the value of CMAKE_TOOLCHAIN_FILE to its
external dependencies, if it's set, so this commit creates two minimal
toolchain files and uses them in the Mac build to set
`CMAKE_OSX_ARCHITECTURES` (and a couple other variables) correctly when
cross-compiling.

a good follow-up would be to see if we can enable Python tests on
arm64 using a macos-14 runner, which is available for public repos:
<https://docs.github.com/en/actions/using-github-hosted-runners/using-github-hosted-runners/about-github-hosted-runners#standard-github-hosted-runners-for-public-repositories>

Signed-off-by: Tom Jakubowski <[email protected]>

cmake/toolchains/darwin-arm64.cmake

@@ -0,0 +1,24 @@
+#  ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
+#  ┃ ██████ ██████ ██████       █      █      █      █      █ █▄  ▀███ █       ┃
+#  ┃ ▄▄▄▄▄█ █▄▄▄▄▄ ▄▄▄▄▄█  ▀▀▀▀▀█▀▀▀▀▀ █ ▀▀▀▀▀█ ████████▌▐███ ███▄  ▀█ █ ▀▀▀▀▀ ┃
+#  ┃ █▀▀▀▀▀ █▀▀▀▀▀ █▀██▀▀ ▄▄▄▄▄ █ ▄▄▄▄▄█ ▄▄▄▄▄█ ████████▌▐███ █████▄   █ ▄▄▄▄▄ ┃
+#  ┃ █      ██████ █  ▀█▄       █ ██████      █      ███▌▐███ ███████▄ █       ┃
+#  ┣━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┫
+#  ┃ Copyright (c) 2017, the Perspective Authors.                              ┃
+#  ┃ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ ┃
+#  ┃ This file is part of the Perspective library, distributed under the terms ┃
+#  ┃ of the [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0). ┃
+#  ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
+
+# Minimal toolchain file to ensure that Arrow's bundled dependency builds use
+# the correct architecture for Mac builds.
+
+# (Arrow does not as of Oct 2024 pass on CMAKE_OSX_ARCHITECTURES to its
+# dependencies if it is set, but does pass on a toolchain file)
+
+set(CMAKE_OSX_ARCHITECTURES "arm64" CACHE STRING "Target architecture for Mac builds")
+# Arrow uses this to choose a `-march` flag
+set(CMAKE_SYSTEM_PROCESSOR "arm64")
+# Prevent cmake from overwriting CMAKE_SYSTEM_PROCESSOR
+# https://github.com/apache/arrow/issues/44448#issuecomment-2418649378
+set(CMAKE_SYSTEM_NAME "Darwin")

cmake/toolchains/darwin-x86_64.cmake

@@ -0,0 +1,24 @@
+#  ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
+#  ┃ ██████ ██████ ██████       █      █      █      █      █ █▄  ▀███ █       ┃
+#  ┃ ▄▄▄▄▄█ █▄▄▄▄▄ ▄▄▄▄▄█  ▀▀▀▀▀█▀▀▀▀▀ █ ▀▀▀▀▀█ ████████▌▐███ ███▄  ▀█ █ ▀▀▀▀▀ ┃
+#  ┃ █▀▀▀▀▀ █▀▀▀▀▀ █▀██▀▀ ▄▄▄▄▄ █ ▄▄▄▄▄█ ▄▄▄▄▄█ ████████▌▐███ █████▄   █ ▄▄▄▄▄ ┃
+#  ┃ █      ██████ █  ▀█▄       █ ██████      █      ███▌▐███ ███████▄ █       ┃
+#  ┣━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┫
+#  ┃ Copyright (c) 2017, the Perspective Authors.                              ┃
+#  ┃ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ ┃
+#  ┃ This file is part of the Perspective library, distributed under the terms ┃
+#  ┃ of the [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0). ┃
+#  ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
+
+# Minimal toolchain file to ensure that Arrow's bundled dependency builds use
+# the correct architecture for Mac builds.
+
+# (Arrow does not as of Oct 2024 pass on CMAKE_OSX_ARCHITECTURES to its
+# dependencies if it is set, but does pass on a toolchain file)
+
+set(CMAKE_OSX_ARCHITECTURES "x86_64" CACHE STRING "Target architecture for Mac builds")
+# Arrow uses this to choose a `-march` flag
+set(CMAKE_SYSTEM_PROCESSOR "x86_64")
+# Prevent cmake from overwriting CMAKE_SYSTEM_PROCESSOR
+# https://github.com/apache/arrow/issues/44448#issuecomment-2418649378
+set(CMAKE_SYSTEM_NAME "Darwin")

rust/perspective-server/build/psp.rs

@@ -26,10 +26,24 @@ pub fn cmake_build() -> Result<Option<PathBuf>, std::io::Error> {
     let profile = std::env::var("PROFILE").unwrap();
     dst.always_configure(true);
     dst.define("CMAKE_BUILD_TYPE", profile.as_str());
-    if std::env::var("PSP_ARCH").as_deref() == Ok("x86_64") {
-        dst.define("CMAKE_OSX_ARCHITECTURES", "x86_64");
-    } else if std::env::var("PSP_ARCH").as_deref() == Ok("arm64") {
-        dst.define("CMAKE_OSX_ARCHITECTURES", "arm64");
+
+    if cfg!(target_os = "macos") {
+        // Set CMAKE_OSX_ARCHITECTURES et al. for Mac builds.  Arrow does not forward on
+        // CMAKE_OSX_ARCHITECTURES and but it does forward on a
+        // CMAKE_TOOLCHAIN_FILE. In Conda builds, the environment sets
+        // `CMAKE_ARGS` up with various toolchain arguments. This block may need
+        // to be patched out or adjusted for Conda.
+        let toolchain_file = match std::env::var("PSP_ARCH").as_deref() {
+            Ok("x86_64") => "./cmake/toolchains/darwin-x86_64.cmake",
+            Ok("aarch64") => "./cmake/toolchains/darwin-arm64.cmake",
+            arch @ Ok(_) | arch @ Err(_) => {
+                panic!("Unknown PSP_ARCH value: {:?}", arch)
+            },
+        };
+        dst.define(
+            "CMAKE_TOOLCHAIN_FILE",
+            std::fs::canonicalize(toolchain_file).expect("Failed to canonicalize toolchain file."),
+        );
     }
 
     if std::env::var("TARGET")