Make update-copy.sh work for both OSX and GNU sed

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

storage/remote/otlptranslator/update-copy.sh

@@ -18,5 +18,10 @@ rm -rf ./prometheus/*_test.go
 
 rm -rf ./tmp
 
-sed -i 's#github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus#github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheus#g' ./prometheusremotewrite/*.go
+case $(sed --help 2>&1) in
-sed -i '1s#^#// DO NOT EDIT. COPIED AS-IS. SEE ../README.md\n\n#g' ./prometheusremotewrite/*.go ./prometheus/*.go
+  *GNU*) set sed -i;;
+  *)     set sed -i '';;
+esac
+
+"$@" -e 's#github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus#github.com/prometheus/prometheus/storage/remote/otlptranslator/prometheus#g' ./prometheusremotewrite/*.go
+"$@" -e '1s#^#// DO NOT EDIT. COPIED AS-IS. SEE ../README.md\n\n#g' ./prometheusremotewrite/*.go ./prometheus/*.go