Merge pull request #54001 from cblecker/sed-func

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Extract gnu-sed detection into a function

**What this PR does / why we need it**:
Moves gnu-sed detection into a reusable function across scripts (considering it's in multiple places).

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:
```release-note
NONE
```

hack/lib/util.sh

@@ -775,6 +775,23 @@ function kube::util::ensure_dockerized {
   fi
 }
 
+# kube::util::ensure-gnu-sed
+# Determines which sed binary is gnu-sed on linux/darwin
+#
+# Sets:
+#  SED: The name of the gnu-sed binary
+#
+function kube::util::ensure-gnu-sed {
+  if LANG=C sed --help 2>&1 | grep -q GNU; then
+    SED="sed"
+  elif which gsed &>/dev/null; then
+    SED="gsed"
+  else
+    kube::log::error "Failed to find GNU sed as sed or gsed. If you are on Mac: brew install gnu-sed." >&2
+    return 1
+  fi
+}
+
 # Some useful colors.
 if [[ -z "${color_start-}" ]]; then
   declare -r color_start="\033["