Move --linkopt flags into user_link_flags

Previous behavior was to put flags coming from Bazel option --linkopt into
legacy_link_flags. They should be in user_link_flags instead (together with
flags coming from linkopts rule attribute). This cl introduces
--experimental_linkopts_in_user_link_flags option that flips the behavior.

There is another incompatible change. Previously cc_common.create_link_variables() included flags from --linkopt, with the flag flipped it doesn't anymore. I believe
--linkopt flags shouldn't be there by default because:
* We don't tie the API with the specifics of C++ rules/options, enabling theoretical use with other languages (objc)
* Users are free to use ctx.fragments.cpp to access C++ options and add them explicitly (https://github.com/bazelbuild/bazel/issues/5602)
* New behavior maintains the symmetry with --copt and user_compile_flags

RELNOTES: None.
PiperOrigin-RevId: 205274272

1 files changed, 11 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
index 56bca06241..8a99e731a3 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
@@ -926,6 +926,16 @@ public class CppLinkActionBuilder {
 
     CcToolchainVariables variables;
     try {
+      ImmutableList<String> userLinkFlags;
+      if (cppConfiguration.enableLinkoptsInUserLinkFlags()) {
+        userLinkFlags =
+            ImmutableList.<String>builder()
+                .addAll(linkopts)
+                .addAll(toolchain.getLinkOptions())
+                .build();
+      } else {
+        userLinkFlags = ImmutableList.copyOf(linkopts);
+      }
       variables =
           LinkBuildVariables.setupVariables(
               getLinkType().linkerOrArchiver().equals(LinkerOrArchiver.LINKER),
@@ -941,7 +951,7 @@ public class CppLinkActionBuilder {
               featureConfiguration,
               useTestOnlyFlags,
               isLtoIndexing,
-              ImmutableList.copyOf(linkopts),
+              userLinkFlags,
               toolchain.getInterfaceSoBuilder().getExecPathString(),
               interfaceOutput != null ? interfaceOutput.getExecPathString() : null,
               ltoOutputRootPrefix,