Don't build twice the sanitizers on Linux

This commit is an attempted fix at #50887. It was noticed that on that issue
we're building both x86_64 and i386 versions of libraries, but we only actually
need the x86_64 versions! This hopes that the build race condition exhibited
in #50887 is connected to building both architectures and/or building a lot of
libraries, so this should help us build precisely what we need and no more.

src/build_helper/lib.rs

@@ -15,6 +15,7 @@ use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 use std::time::{SystemTime, UNIX_EPOCH};
 use std::{env, fs};
+use std::thread;
 
 /// A helper macro to `unwrap` a result except also print out details like:
 ///
@@ -181,7 +182,9 @@ pub struct NativeLibBoilerplate {
 
 impl Drop for NativeLibBoilerplate {
     fn drop(&mut self) {
-        t!(File::create(self.out_dir.join("rustbuild.timestamp")));
+        if !thread::panicking() {
+            t!(File::create(self.out_dir.join("rustbuild.timestamp")));
+        }
     }
 }
 
@@ -225,24 +228,34 @@ pub fn native_lib_boilerplate(
     }
 }
 
-pub fn sanitizer_lib_boilerplate(sanitizer_name: &str) -> Result<NativeLibBoilerplate, ()> {
-    let (link_name, search_path) = match &*env::var("TARGET").unwrap() {
+pub fn sanitizer_lib_boilerplate(sanitizer_name: &str)
+    -> Result<(NativeLibBoilerplate, String), ()>
+{
+    let (link_name, search_path, dynamic) = match &*env::var("TARGET").unwrap() {
         "x86_64-unknown-linux-gnu" => (
             format!("clang_rt.{}-x86_64", sanitizer_name),
             "build/lib/linux",
+            false,
         ),
         "x86_64-apple-darwin" => (
-            format!("dylib=clang_rt.{}_osx_dynamic", sanitizer_name),
+            format!("clang_rt.{}_osx_dynamic", sanitizer_name),
             "build/lib/darwin",
+            true,
         ),
         _ => return Err(()),
     };
-    native_lib_boilerplate(
+    let to_link = if dynamic {
+        format!("dylib={}", link_name)
+    } else {
+        format!("static={}", link_name)
+    };
+    let lib = native_lib_boilerplate(
         "libcompiler_builtins/compiler-rt",
         sanitizer_name,
-        &link_name,
+        &to_link,
         search_path,
-    )
+    )?;
+    Ok((lib, link_name))
 }
 
 fn dir_up_to_date(src: &Path, threshold: SystemTime) -> bool {

src/librustc_asan/build.rs

@@ -18,7 +18,7 @@ use cmake::Config;
 
 fn main() {
     if let Some(llvm_config) = env::var_os("LLVM_CONFIG") {
-        let native = match sanitizer_lib_boilerplate("asan") {
+        let (native, target) = match sanitizer_lib_boilerplate("asan") {
             Ok(native) => native,
             _ => return,
         };
@@ -29,7 +29,7 @@ fn main() {
             .define("COMPILER_RT_BUILD_XRAY", "OFF")
             .define("LLVM_CONFIG_PATH", llvm_config)
             .out_dir(&native.out_dir)
-            .build_target("asan")
+            .build_target(&target)
             .build();
     }
     println!("cargo:rerun-if-env-changed=LLVM_CONFIG");

src/librustc_lsan/build.rs

@@ -18,7 +18,7 @@ use cmake::Config;
 
 fn main() {
     if let Some(llvm_config) = env::var_os("LLVM_CONFIG") {
-        let native = match sanitizer_lib_boilerplate("lsan") {
+        let (native, target) = match sanitizer_lib_boilerplate("lsan") {
             Ok(native) => native,
             _ => return,
         };
@@ -29,7 +29,7 @@ fn main() {
             .define("COMPILER_RT_BUILD_XRAY", "OFF")
             .define("LLVM_CONFIG_PATH", llvm_config)
             .out_dir(&native.out_dir)
-            .build_target("lsan")
+            .build_target(&target)
             .build();
     }
     println!("cargo:rerun-if-env-changed=LLVM_CONFIG");

src/librustc_msan/build.rs

@@ -18,7 +18,7 @@ use cmake::Config;
 
 fn main() {
     if let Some(llvm_config) = env::var_os("LLVM_CONFIG") {
-        let native = match sanitizer_lib_boilerplate("msan") {
+        let (native, target) = match sanitizer_lib_boilerplate("msan") {
             Ok(native) => native,
             _ => return,
         };
@@ -29,7 +29,7 @@ fn main() {
             .define("COMPILER_RT_BUILD_XRAY", "OFF")
             .define("LLVM_CONFIG_PATH", llvm_config)
             .out_dir(&native.out_dir)
-            .build_target("msan")
+            .build_target(&target)
             .build();
     }
     println!("cargo:rerun-if-env-changed=LLVM_CONFIG");

src/librustc_tsan/build.rs

@@ -18,7 +18,7 @@ use cmake::Config;
 
 fn main() {
     if let Some(llvm_config) = env::var_os("LLVM_CONFIG") {
-        let native = match sanitizer_lib_boilerplate("tsan") {
+        let (native, target) = match sanitizer_lib_boilerplate("tsan") {
             Ok(native) => native,
             _ => return,
         };
@@ -29,7 +29,7 @@ fn main() {
             .define("COMPILER_RT_BUILD_XRAY", "OFF")
             .define("LLVM_CONFIG_PATH", llvm_config)
             .out_dir(&native.out_dir)
-            .build_target("tsan")
+            .build_target(&target)
             .build();
     }
     println!("cargo:rerun-if-env-changed=LLVM_CONFIG");