Latest versions break rust-lang bootstrap

[lasiotus]

PR rust-lang/rust#134344 that only bumps cc and cmake versions fails due to a cmake error (it seems).

[clubby789]

Specifically d668808#diff-b1a35a68f14e696205874893c07fd24fdb88882b47c23cc0e0c80a30c7d53759R458

This may be a bootstrap bug, I'll try and look into it

[jieyouxu]

Bisection was done at rust-lang/rust#134558.

2024-12-16T08:24:34.9104890Z could not determine CMAKE_SYSTEM_NAME from the target `aarch64-apple-ios`, build may fail
2024-12-16T08:24:34.9107480Z CMAKE_TOOLCHAIN_FILE_aarch64-apple-ios = None
2024-12-16T08:24:34.9109170Z CMAKE_TOOLCHAIN_FILE_aarch64_apple_ios = None
2024-12-16T08:24:34.9111250Z TARGET_CMAKE_TOOLCHAIN_FILE = None
2024-12-16T08:24:34.9116590Z CMAKE_TOOLCHAIN_FILE = None
2024-12-16T08:24:34.9120130Z thread 'main' panicked at /Users/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/cmake-0.1.52/src/lib.rs:1115:5:
2024-12-16T08:24:34.9121100Z 
2024-12-16T08:24:34.9121380Z environment variable `CARGO_CFG_TARGET_OS` not defined
2024-12-16T08:24:34.9121820Z 
2024-12-16T08:24:34.9122030Z build script failed, must exit now

It seems that somehow CARGO_CFG_TARGET_OS isn't available.

[jieyouxu]

Hm, according to cargo docs, CARGO_CFG_* family of flags are only set for build scripts (by cargo), but d668808#diff-b1a35a68f14e696205874893c07fd24fdb88882b47c23cc0e0c80a30c7d53759R458 seemed to unconditionally expect that env var to be available from the environment, but it is not a build script.

But cmake-rs is only used from build env, so that shouldn't be a problem...

[clubby789]

cmake-rs/src/lib.rs

Lines 459 to 462 in 94da9de

	} else if target != host && !self.defined("CMAKE_SYSTEM_NAME") {
	// Set CMAKE_SYSTEM_NAME and CMAKE_SYSTEM_PROCESSOR when cross compiling
	let os = getenv_unwrap("CARGO_CFG_TARGET_OS");
	let arch = getenv_unwrap("CARGO_CFG_TARGET_ARCH");

These lines expect cmake to be used from a build script, but bootstrap uses it as a runtime library. Feel free to close if this isn't a supported use case - we can fix this from our end by defining the correct CMAKE_SYSTEM_NAME.