vpython: only run uname once

Bug: 1469696
Change-Id: I3a055c0704e8da586c16b3c1a3e0758c398f614b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4745141
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Chenlin Fan <fancl@chromium.org>
Reviewed-by: Chenlin Fan <fancl@chromium.org>

vpython

@@ -41,8 +41,11 @@ base_dir=$(dirname "$0")
 source "$base_dir/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
-if [[ $(uname -s) = MINGW* || $(uname -s) = CYGWIN* ]]; then
+case $(uname -s) in
+MINGW*|CYGWIN*)
   cmd.exe //c $0.bat "$@"
-else
+  ;;
+*)
   exec "$base_dir/.cipd_bin/vpython" "$@"
-fi
+  ;;
+esac

vpython3

@@ -39,8 +39,11 @@ base_dir=$(dirname "$0")
 source "$base_dir/cipd_bin_setup.sh"
 cipd_bin_setup &> /dev/null
 
-if [[ $(uname -s) = MINGW* || $(uname -s) = CYGWIN* ]]; then
+case $(uname -s) in
+MINGW*|CYGWIN*)
   cmd.exe //c $0.bat "$@"
-else
+  ;;
+*)
   exec "$base_dir/.cipd_bin/vpython3" "$@"
-fi
+  ;;
+esac