skip bootstrap target sanity checks when testing Miri

src/bootstrap/sanity.rs

@@ -155,6 +155,11 @@ than building it.
             continue;
         }
 
+        // Some environments don't want or need these tools, such as when testing Miri.
+        if env::var_os("BOOTSTRAP_SKIP_TARGET_SANITY").is_some() {
+            continue;
+        }
+
         if !build.config.dry_run {
             cmd_finder.must_have(build.cc(*target));
             if let Some(ar) = build.ar(*target) {
@@ -212,6 +217,11 @@ than building it.
             }
         }
 
+        // Some environments don't want or need these tools, such as when testing Miri.
+        if env::var_os("BOOTSTRAP_SKIP_TARGET_SANITY").is_some() {
+            continue;
+        }
+
         if need_cmake && target.contains("msvc") {
             // There are three builds of cmake on windows: MSVC, MinGW, and
             // Cygwin. The Cygwin build does not have generators for Visual

src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh

@@ -27,10 +27,7 @@ python3 "$X_PY" test --stage 2 src/tools/rustfmt
 python3 "$X_PY" test --stage 2 src/tools/miri
 # We natively run this script on x86_64-unknown-linux-gnu and x86_64-pc-windows-msvc.
 # Also cover some other targets (on both of these hosts) via cross-testing.
-#
-# Currently disabled -- we end up pulling in a cross-compile of LLVM (maybe
-# just overly eager sanity checks), but in any case this won't work when
-# building LLVM as of this comment.
-#python3 "$X_PY" test --stage 2 src/tools/miri --target i686-pc-windows-msvc
-#FIXME(/~https://github.com/rust-lang/rust/issues/103519): macOS testing is currently disabled
-# python3 "$X_PY" test --stage 2 src/tools/miri --target aarch64-apple-darwin
+export BOOTSTRAP_SKIP_TARGET_SANITY=1 # we don't need `cc` for these targets
+python3 "$X_PY" test --stage 2 src/tools/miri --target i686-pc-windows-msvc
+python3 "$X_PY" test --stage 2 src/tools/miri --target aarch64-apple-darwin
+unset BOOTSTRAP_SKIP_TARGET_SANITY