From 6b9af8cb36d2bc1ae57768e3c8703093870d919f Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Mon, 29 May 2023 13:18:41 +0000
Subject: [PATCH] Disable all incremental compilation for
 CARGO_BUILD_INCREMENTAL=false

---
 build_system/build_backend.rs |  8 ++------
 build_system/build_sysroot.rs |  8 ++------
 build_system/utils.rs         | 10 ++++++++++
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/build_system/build_backend.rs b/build_system/build_backend.rs
index b88489a341c..6855c1a7fc5 100644
--- a/build_system/build_backend.rs
+++ b/build_system/build_backend.rs
@@ -3,7 +3,7 @@
 
 use super::path::{Dirs, RelPath};
 use super::rustc_info::get_file_name;
-use super::utils::{is_ci, is_ci_opt, CargoProject, Compiler};
+use super::utils::{is_ci, is_ci_opt, maybe_incremental, CargoProject, Compiler};
 
 pub(crate) static CG_CLIF: CargoProject = CargoProject::new(&RelPath::SOURCE, "cg_clif");
 
@@ -14,8 +14,7 @@ pub(crate) fn build_backend(
     use_unstable_features: bool,
 ) -> PathBuf {
     let mut cmd = CG_CLIF.build(&bootstrap_host_compiler, dirs);
-
-    cmd.env("CARGO_BUILD_INCREMENTAL", "true"); // Force incr comp even in release mode
+    maybe_incremental(&mut cmd);
 
     let mut rustflags = env::var("RUSTFLAGS").unwrap_or_default();
 
@@ -23,9 +22,6 @@ pub(crate) fn build_backend(
         // Deny warnings on CI
         rustflags += " -Dwarnings";
 
-        // Disabling incr comp reduces cache size and incr comp doesn't save as much on CI anyway
-        cmd.env("CARGO_BUILD_INCREMENTAL", "false");
-
         if !is_ci_opt() {
             cmd.env("CARGO_PROFILE_RELEASE_DEBUG_ASSERTIONS", "true");
             cmd.env("CARGO_PROFILE_RELEASE_OVERFLOW_CHECKS", "true");
diff --git a/build_system/build_sysroot.rs b/build_system/build_sysroot.rs
index 5ea34f758b9..04cd3894adc 100644
--- a/build_system/build_sysroot.rs
+++ b/build_system/build_sysroot.rs
@@ -5,7 +5,7 @@
 use super::path::{Dirs, RelPath};
 use super::rustc_info::{get_file_name, get_rustc_version};
 use super::utils::{
-    is_ci, remove_dir_if_exists, spawn_and_wait, try_hard_link, CargoProject, Compiler,
+    maybe_incremental, remove_dir_if_exists, spawn_and_wait, try_hard_link, CargoProject, Compiler,
 };
 use super::{CodegenBackend, SysrootKind};
 
@@ -274,11 +274,7 @@ fn build_clif_sysroot_for_triple(
     }
     compiler.rustflags += &rustflags;
     let mut build_cmd = STANDARD_LIBRARY.build(&compiler, dirs);
-    build_cmd.env("CARGO_BUILD_INCREMENTAL", "true"); // Force incr comp even in release mode
-    if is_ci() {
-        // Disabling incr comp reduces cache size and incr comp doesn't save as much on CI anyway
-        build_cmd.env("CARGO_BUILD_INCREMENTAL", "false");
-    }
+    maybe_incremental(&mut build_cmd);
     if channel == "release" {
         build_cmd.arg("--release");
     }
diff --git a/build_system/utils.rs b/build_system/utils.rs
index e7fcb2644d7..41fc366e290 100644
--- a/build_system/utils.rs
+++ b/build_system/utils.rs
@@ -258,3 +258,13 @@ pub(crate) fn is_ci() -> bool {
 pub(crate) fn is_ci_opt() -> bool {
     env::var("CI_OPT").is_ok()
 }
+
+pub(crate) fn maybe_incremental(cmd: &mut Command) {
+    if is_ci() || std::env::var("CARGO_BUILD_INCREMENTAL").map_or(false, |val| val == "false") {
+        // Disabling incr comp reduces cache size and incr comp doesn't save as much on CI anyway
+        cmd.env("CARGO_BUILD_INCREMENTAL", "false");
+    } else {
+        // Force incr comp even in release mode unless in CI or incremental builds are explicitly disabled
+        cmd.env("CARGO_BUILD_INCREMENTAL", "true");
+    }
+}