[MWRAPPER-113] mvnw.cmd PowerShell error and surrounding empty lines …

…go to standard output

Use Write-Error instead of Write-Output in the PowerShell part.
Also redirect the empty lines that surround error messages to stderr.

maven-wrapper-distribution/src/resources/mvnw.cmd

@@ -59,22 +59,22 @@ set ERROR_CODE=0
 @REM ==== START VALIDATION ====
 if not "%JAVA_HOME%" == "" goto OkJHome
 
-echo.
+echo. >&2
 echo Error: JAVA_HOME not found in your environment. >&2
 echo Please set the JAVA_HOME variable in your environment to match the >&2
 echo location of your Java installation. >&2
-echo.
+echo. >&2
 goto error
 
 :OkJHome
 if exist "%JAVA_HOME%\bin\java.exe" goto init
 
-echo.
+echo. >&2
 echo Error: JAVA_HOME is set to an invalid directory. >&2
 echo JAVA_HOME = "%JAVA_HOME%" >&2
 echo Please set the JAVA_HOME variable in your environment to match the >&2
 echo location of your Java installation. >&2
-echo.
+echo. >&2
 goto error
 
 @REM ==== END VALIDATION ====
@@ -162,9 +162,9 @@ IF NOT %WRAPPER_SHA_256_SUM%=="" (
     powershell -Command "&{"^
        "$hash = (Get-FileHash \"%WRAPPER_JAR%\" -Algorithm SHA256).Hash.ToLower();"^
        "If('%WRAPPER_SHA_256_SUM%' -ne $hash){"^
-       "  Write-Output 'Error: Failed to validate Maven wrapper SHA-256, your Maven wrapper might be compromised.';"^
-       "  Write-Output 'Investigate or delete %WRAPPER_JAR% to attempt a clean download.';"^
-       "  Write-Output 'If you updated your Maven version, you need to update the specified wrapperSha256Sum property.';"^
+       "  Write-Error 'Error: Failed to validate Maven wrapper SHA-256, your Maven wrapper might be compromised.';"^
+       "  Write-Error 'Investigate or delete %WRAPPER_JAR% to attempt a clean download.';"^
+       "  Write-Error 'If you updated your Maven version, you need to update the specified wrapperSha256Sum property.';"^
        "  exit 1;"^
        "}"^
        "}"