bin/mkube: Update according to shellcheck suggestions (#4419)

Also clean up sed Windows path filtering.

Signed-off-by: Joakim Roubert <joakimr@axis.com>

.github/workflows/static_checks.yml

@@ -101,7 +101,6 @@ jobs:
         ! -name lint \
         ! -name _log.sh \
         ! -name minikube-start-hyperv.bat \
-        ! -name mkube \
         ! -name protoc-go.sh \
         ! -name root-tag \
         ! -name _tag.sh \

bin/mkube

@@ -16,6 +16,6 @@ else
 fi
 
 # Rewrite Windows style paths "C:\\whatever\\whatever" to "/mnt/c/whatever/whatever".
-eval $("${MINIKUBE_EXE}" docker-env --shell=bash | sed "s|C:\\\|/mnt/c/|g" | sed "s|\\\|/|g")
+eval "$("${MINIKUBE_EXE}" docker-env --shell=bash | sed 's|C:\\|/mnt/c/|g;s|\\|/|g')"
 
-exec $@
+exec "$@"