dev-lang/rust: Disable LTO by default and use thin

We've had a few issues with lto on, and it isn't on by default generally
among Gentoo packages, so this commit flips it to be off by default.

Additionally, in an upstream ticket[0] it was suggested to use thin LTO
rather than fat LTO, so this commit makes that adjustment as well.

[0] rust-lang/rust#121124

Bug: https://bugs.gentoo.org/924301
Signed-off-by: Randy Barlow <randy@electronsweatshop.com>

dev-lang/rust/rust-1.76.0.ebuild → dev-lang/rust/rust-1.76.0-r1.ebuild

@@ -42,7 +42,7 @@ LLVM_TARGET_USEDEPS=${ALL_LLVM_TARGETS[@]/%/(-)?}
 
 LICENSE="|| ( MIT Apache-2.0 ) BSD BSD-1 BSD-2 BSD-4"
 
-IUSE="big-endian clippy cpu_flags_x86_sse2 debug dist doc llvm-libunwind +lto miri nightly parallel-compiler profiler rustfmt rust-analyzer rust-src system-bootstrap system-llvm test wasm ${ALL_LLVM_TARGETS[*]}"
+IUSE="big-endian clippy cpu_flags_x86_sse2 debug dist doc llvm-libunwind lto miri nightly parallel-compiler profiler rustfmt rust-analyzer rust-src system-bootstrap system-llvm test wasm ${ALL_LLVM_TARGETS[*]}"
 
 # Please keep the LLVM dependency block separate. Since LLVM is slotted,
 # we need to *really* make sure we're not pulling more than one slot
@@ -469,7 +469,8 @@ src_configure() {
 		deny-warnings = $(usex wasm $(usex doc false true) true)
 		backtrace-on-ice = true
 		jemalloc = false
-		lto = "$(usex lto fat off)"
+		# See https://github.com/rust-lang/rust/issues/121124
+		lto = "$(usex lto thin off)"
 		[dist]
 		src-tarball = false
 		compression-formats = ["xz"]