Preserve --experimental_allow_unresolved_symlinks in exec cfg

See bazelbuild#10298 (comment)

Work towards bazelbuild#10298

Closes bazelbuild#15702.

PiperOrigin-RevId: 456480627
Change-Id: Ib1237ce9e2c0bab0d7eabd8743f08ec60b8b7ab7

Author: fmeum

src/main/java/com/google/devtools/build/lib/analysis/config/CoreOptions.java

@@ -947,6 +947,7 @@ public FragmentOptions getHost() {
     host.archivedArtifactsMnemonicsFilter = archivedArtifactsMnemonicsFilter;
 
     host.enableAspectHints = enableAspectHints;
+    host.allowUnresolvedSymlinks = allowUnresolvedSymlinks;
 
     return host;
   }

src/test/shell/bazel/bazel_symlink_test.sh

@@ -584,4 +584,21 @@ EOF
   expect_log "cycle in dependency graph"
 }
 
+function test_unresolved_symlink_in_exec_cfg() {
+  mkdir -p a
+  cat > a/BUILD <<'EOF'
+load("//symlink:symlink.bzl", "dangling_symlink")
+dangling_symlink(name="a", link_target="non/existent")
+genrule(
+    name = "exec",
+    srcs = [],
+    outs = ["out"],
+    cmd = "touch $@",
+    exec_tools = [":a"],
+)
+EOF
+
+  bazel --windows_enable_symlinks build --experimental_allow_unresolved_symlinks //a:exec || fail "build failed"
+}
+
 run_suite "Tests for symlink artifacts"