[BUG] Suspicious warnings building on windows (unmappable character (0x90) for encoding windows-1252)

[dblock]

Describe the bug

Building the plugin on Windows produces suspicious warnings.

To Reproduce

./gradlew build

> Task :legacy:compileJava
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\domain\Condition.java:41: error: unmappable character (0x9D) for encoding windows-1252
 * 过滤�件
          ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\domain\Field.java:36: error: unmappable character (0x90) for encoding windows-1252
 * �索域
    ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\domain\MethodField.java:37: error: unmappable character (0x90) for encoding windows-1252
 * �索域
    ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\domain\Order.java:30: error: unmappable character (0x8F) for encoding windows-1252
 * 排�规�
        ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\domain\SearchResult.java:105: error: unmappable character (0x8D) for encoding windows-1252
     * 讲es的field域转�为你Object
                           ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\domain\SearchResult.java:124: error: unmappable character (0x8D) for encoding windows-1252
     * 讲es的field域转�为你Object
                           ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\domain\Select.java:41: error: unmappable character (0x8F) for encoding windows-1252
 * 将sql语�转�为select 对象
             ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\domain\Select.java:41: error: unmappable character (0x8D) for encoding windows-1252
 * 将sql语�转�为select 对象
                   ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\parser\FieldMaker.java:64: error: unmappable character (0x8F) for encoding windows-1252
 * 一些具有�数的一�在 select 函数.�者group by 函数
                ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\query\maker\AggMaker.java:94: error: unmappable character (0x81) for encoding windows-1252
     * �组查的��函数
                    ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\query\maker\AggMaker.java:94: error: unmappable character (0x90) for encoding windows-1252
     * �组查的��函数
                       ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\query\maker\Maker.java:116: error: unmappable character (0x9D) for encoding windows-1252
     * 构建过滤�件
                    ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\query\maker\QueryMaker.java:42: error: unmappable character (0x9D) for encoding windows-1252
     * 将where�件构建�query
                ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\query\maker\QueryMaker.java:42: error: unmappable character (0x90) for encoding windows-1252
     * 将where�件构建�query
                             ^
C:\Users\Administrator\AppData\Local\Temp\2\tmpovd5v0gr\sql\legacy\src\main\java\org\opensearch\sql\legacy\query\maker\QueryMaker.java:81: error: unmappable character (0x8F) for encoding windows-1252
     * 增加嵌套�
                    ^

Host/Environment (please complete the following information):
MINGW64_NT-10.0-17763 EC2AMAZ-4PA8CKB 3.1.7-340.x86_64 2021-10-12 16:29 UTC x86_64 Msys

Additional context
Coming from opensearch-project/opensearch-build#33

[anirudha]

When not setting the compiler encoding option explicitly, the problem you can run into is, that the Java compiler uses a different file encoding. we should edit the build gradle to set correct compiler encodings