make kube::util::find-binary not dependent on bazel-out/ structure

Implement an aspect that outputs go_build_mode metadata for go binaries,
and use that during binary selection.

build/go.bzl

@@ -12,7 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_test")
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_context", "go_test")
+load("@io_bazel_rules_go//go/platform:list.bzl", "GOOS_GOARCH")
 
 # Defines a go_binary rule that enables cgo on platform builds targeting Linux,
 # and otherwise builds a pure go binary.
@@ -47,3 +48,64 @@ def go_test_conditional_pure(name, out, tags = [], **kwargs):
         name = "name",
         actual = out,
     )
+
+_GO_BUILD_MODE_TMPL = "{goos}/{goarch}/pure={pure},static={static},msan={msan},race={race}\n"
+
+def _go_build_mode_aspect_impl(target, ctx):
+    if (not hasattr(ctx.rule.attr, "_is_executable") or
+        not ctx.rule.attr._is_executable or
+        ctx.rule.attr.testonly):
+        # We only care about exporting platform info for executable targets
+        # that aren't testonly (e.g. kubectl and e2e.test).
+        return []
+
+    mode = go_context(ctx).mode
+
+    out = ctx.actions.declare_file(
+        target.files_to_run.executable.basename + ".go_build_mode",
+        sibling = target.files_to_run.executable,
+    )
+    ctx.actions.write(out, _GO_BUILD_MODE_TMPL.format(
+        goos = mode.goos,
+        goarch = mode.goarch,
+        pure = str(mode.pure).lower(),
+        static = str(mode.static).lower(),
+        msan = str(mode.msan).lower(),
+        race = str(mode.race).lower(),
+    ))
+
+    return [OutputGroupInfo(default = depset([out]))]
+
+# This aspect ouputs a *.go_build_mode metadata for go binaries. This metadata
+# is used for executable selection e.g. in CI.
+go_build_mode_aspect = aspect(
+    implementation = _go_build_mode_aspect_impl,
+    attrs = {
+        "goos": attr.string(
+            default = "auto",
+            values = ["auto"] + {goos: None for goos, _ in GOOS_GOARCH}.keys(),
+        ),
+        "goarch": attr.string(
+            default = "auto",
+            values = ["auto"] + {goarch: None for _, goarch in GOOS_GOARCH}.keys(),
+        ),
+        "pure": attr.string(
+            default = "auto",
+            values = ["auto", "on", "off"],
+        ),
+        "static": attr.string(
+            default = "auto",
+            values = ["auto", "on", "off"],
+        ),
+        "msan": attr.string(
+            default = "auto",
+            values = ["auto", "on", "off"],
+        ),
+        "race": attr.string(
+            default = "auto",
+            values = ["auto", "on", "off"],
+        ),
+        "_go_context_data": attr.label(default = "@io_bazel_rules_go//:go_context_data"),
+    },
+    toolchains = ["@io_bazel_rules_go//go:toolchain"],
+)

build/root/.bazelrc

@@ -22,6 +22,10 @@ build --define gotags=selinux
 # This flag requires Bazel 0.5.0+
 build --sandbox_fake_username
 
+# Output go_build_mode metadata for binaries. This metadata is used for
+# executable selection e.g. in CI.
+build --aspects //build:go.bzl%go_build_mode_aspect
+
 # Enable go race detection.
 build:unit --@io_bazel_rules_go//go/config:race
 test:unit --@io_bazel_rules_go//go/config:race

hack/lib/util.sh

@@ -207,19 +207,16 @@ kube::util::find-binary-for-platform() {
       "${KUBE_ROOT}/_output/dockerized/go/bin/${lookfor}"
     );
   fi
-  # Also search for binary in bazel build tree.
-  # The bazel go rules place some binaries in subtrees like
-  # "bazel-bin/source/path/linux_amd64_pure_stripped/binaryname", so make sure
-  # the platform name is matched in the path.
-  while IFS=$'\n' read -r location; do
-    locations+=("$location");
-  done < <(find "${KUBE_ROOT}/bazel-bin/" -type f -executable \
-    \( -path "*/${platform/\//_}*/${lookfor}" -o -path "*/${lookfor}" \) 2>/dev/null || true)
-  # search for executables for non-GNU versions of find (eg. BSD)
-  while IFS=$'\n' read -r location; do
-    locations+=("$location");
-  done < <(find "${KUBE_ROOT}/bazel-bin/" -type f -perm -111 \
-    \( -path "*/${platform/\//_}*/${lookfor}" -o -path "*/${lookfor}" \) 2>/dev/null || true)
+
+  # Also search for binary in bazel build tree if bazel-out/ exists.
+  if [[ -d "${KUBE_ROOT}/bazel-out" ]]; then
+    while IFS=$'\n' read -r bin_build_mode; do
+      if grep -q "${platform}" "${bin_build_mode}"; then
+        # drop the extension to get the real binary path.
+        locations+=("${bin_build_mode%.*}")
+      fi
+    done < <(find "${KUBE_ROOT}/bazel-out/" -name "${lookfor}.go_build_mode")
+  fi
 
   # List most recently-updated location.
   local -r bin=$( (ls -t "${locations[@]}" 2>/dev/null || true) | head -1 )