Appveyor fix (#815)

Author: gnodet

appveyor.yml

@@ -5,12 +5,12 @@ install:
       Add-Type -AssemblyName System.IO.Compression.FileSystem
       if (!(Test-Path -Path "C:\maven" )) {
         (new-object System.Net.WebClient).DownloadFile(
-          'https://archive.apache.org/dist/maven/maven-3/3.3.9/binaries/apache-maven-3.3.9-bin.zip',
+          'https://archive.apache.org/dist/maven/maven-3/3.8.7/binaries/apache-maven-3.8.7-bin.zip',
           'C:\maven-bin.zip'
         )
         [System.IO.Compression.ZipFile]::ExtractToDirectory("C:\maven-bin.zip", "C:\maven")
       }
-  - cmd: SET M2_HOME=C:\maven\apache-maven-3.3.9
+  - cmd: SET M2_HOME=C:\maven\apache-maven-3.8.7
   - cmd: SET PATH=%M2_HOME%\bin;%JAVA_HOME%\bin;%PATH%
   - cmd: SET MAVEN_OPTS=-XX:MaxPermSize=2g -Xmx4g
   - cmd: SET JAVA_OPTS=-XX:MaxPermSize=2g -Xmx4g