Limited the number of parallel link jobs during LLVM build for mingw.

This is an attempt to fix the spurious build error tracked by
#108227.

Author: michaelwoerister

Diff for: src/ci/run.sh

@@ -59,6 +59,14 @@ RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --enable-locked-deps"
 RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --enable-cargo-native-static"
 RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set rust.codegen-units-std=1"
 
+# When building for mingw, limit the number of parallel linker jobs during
+# the LLVM build, as not to run out of memory.
+# This is an attempt to fix the spurious build error tracked by
+# https://github.com/rust-lang/rust/issues/108227.
+if isWindows && [[ ${CUSTOM_MINGW-0} -eq 1 ]]; then
+    RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set llvm.link-jobs=4"
+fi
+
 # Only produce xz tarballs on CI. gz tarballs will be generated by the release
 # process by recompressing the existing xz ones. This decreases the storage
 # space required for CI artifacts.