Add MSYS2 detection on Windows Terminal (#117612)

As the results of "uname -s" command is like the below on MSYS2 on
Windows Terminal,

MSYS_NT-10.0-22621

This patch fixes the Flutter command working on this kind of systems.
Signed-off-by: Deokgyu Yang <secugyu@gmail.com>
Signed-off-by: Deokgyu Yang <secugyu@gmail.com>

bin/dart

@@ -48,7 +48,7 @@ BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
 OS="$(uname -s)"
 
 # If we're on Windows, invoke the batch script instead to get proper locking.
-if [[ $OS =~ MINGW.* || $OS =~ CYGWIN.* ]]; then
+if [[ $OS =~ MINGW.* || $OS =~ CYGWIN.* || $OS =~ MSYS.* ]]; then
   exec "${BIN_DIR}/dart.bat" "$@"
 fi
 

bin/flutter

@@ -53,7 +53,7 @@ BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
 OS="$(uname -s)"
 
 # If we're on Windows, invoke the batch script instead to get proper locking.
-if [[ $OS =~ MINGW.* || $OS =~ CYGWIN.* ]]; then
+if [[ $OS =~ MINGW.* || $OS =~ CYGWIN.* || $OS =~ MSYS.* ]]; then
   exec "${BIN_DIR}/flutter.bat" "$@"
 fi
 

bin/internal/shared.sh

@@ -200,7 +200,7 @@ function shared::execute() {
   # If running over git-bash, overrides the default UNIX executables with win32
   # executables
   case "$(uname -s)" in
-    MINGW*)
+    MINGW* | MSYS* )
       DART="$DART.exe"
       ;;
   esac

bin/internal/update_dart_sdk.sh

@@ -102,7 +102,7 @@ if [ ! -f "$ENGINE_STAMP" ] || [ "$ENGINE_VERSION" != `cat "$ENGINE_STAMP"` ]; t
       DART_ZIP_NAME="dart-sdk-linux-${ARCH}.zip"
       IS_USER_EXECUTABLE="-perm /u+x"
       ;;
-    MINGW*)
+    MINGW* | MSYS* )
       DART_ZIP_NAME="dart-sdk-windows-x64.zip"
       IS_USER_EXECUTABLE="-perm /u+x"
       ;;