Fixing Windows build using CMake (#7854)
Summary:
Builds were not producing Windows binaries properly in 6.15 branch:
```
00:00:46.413 Tests run: 11, Failures: 0, Errors: 2, Skipped: 0, Time elapsed: 0.183 sec <<< FAILURE! - in org.rocksdb.EventListenerTest
00:00:46.414 testAllCallbacksInvocation(org.rocksdb.EventListenerTest) Time elapsed: 0.012 sec <<< ERROR!
00:00:46.414 java.lang.UnsatisfiedLinkError: org.rocksdb.test.TestableEventListener.invokeAllCallbacks(J)V
00:00:46.414 at org.rocksdb.test.TestableEventListener.invokeAllCallbacks(Native Method)
00:00:46.414 at org.rocksdb.test.TestableEventListener.invokeAllCallbacks(TestableEventListener.java:19)
00:00:46.414 at org.rocksdb.EventListenerTest.testAllCallbacksInvocation(EventListenerTest.java:436)
```
```
00:00:41.497 "D:\j\workspace\RocksDB_Build_Windows\build\java\rocksdbjni_headers.vcxproj" (default target) (3) ->
00:00:41.497 (CustomBuild target) ->
00:00:41.497 CUSTOMBUILD : error : Could not find class file for 'org.rocksdb.TestableEventListener'. [D:\j\workspace\RocksDB_Build_Windows\build\java\rocksdbjni_headers.vcxproj]
```
Also failed on Linux as library was not initialized yet:
```
00:01:25.103 Running org.rocksdb.NativeComparatorWrapperTest
00:01:25.133 Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.006 sec <<< FAILURE! - in org.rocksdb.NativeComparatorWrapperTest
00:01:25.133 rountrip(org.rocksdb.NativeComparatorWrapperTest) Time elapsed: 0.002 sec <<< ERROR!
00:01:25.133 java.lang.UnsatisfiedLinkError: org.rocksdb.NativeComparatorWrapperTest$NativeStringComparatorWrapper.newStringComparator()J
00:01:25.133 at org.rocksdb.NativeComparatorWrapperTest$NativeStringComparatorWrapper.newStringComparator(Native Method)
00:01:25.133 at org.rocksdb.NativeComparatorWrapperTest$NativeStringComparatorWrapper.initializeNative(NativeComparatorWrapperTest.java:87)
00:01:25.133 at org.rocksdb.RocksCallbackObject.<init>(RocksCallbackObject.java:28)
00:01:25.133 at org.rocksdb.AbstractComparator.<init>(AbstractComparator.java:20)
00:01:25.133 at org.rocksdb.NativeComparatorWrapper.<init>(NativeComparatorWrapper.java:16)
00:01:25.133 at org.rocksdb.NativeComparatorWrapperTest$NativeStringComparatorWrapper.<init>(NativeComparatorWrapperTest.java:82)
00:01:25.133 at org.rocksdb.NativeComparatorWrapperTest.rountrip(NativeComparatorWrapperTest.java:30)
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7854
Reviewed By: jay-zhuang
Differential Revision: D25873378
Pulled By: ajkr
fbshipit-source-id: 88afb08bfd30edff31f17da063e636df0769cbfe
d76a8eeef7