Help the build system find system RocksDB.

Taken from this upstream commit:
https://github.com/ceph/ceph/commit/2ac26bd0e01fd6c82bd59936cf25c25173f7775a

diff --git a/cmake/modules/Findrocksdb.cmake b/cmake/modules/Findrocksdb.cmake
index f8369f73fc..5926647348 100644
--- a/cmake/modules/Findrocksdb.cmake
+++ b/cmake/modules/Findrocksdb.cmake
@@ -15,11 +15,11 @@ find_library(ROCKSDB_LIBRARIES rocksdb)
 
 if(ROCKSDB_INCLUDE_DIR AND EXISTS "${ROCKSDB_INCLUDE_DIR}/rocksdb/version.h")
   foreach(ver "MAJOR" "MINOR" "PATCH")
-    file(STRINGS "${ROCKSDB_INCLUDE_DIR}/version.h" ROCKSDB_VER_${ver}_LINE
+    file(STRINGS "${ROCKSDB_INCLUDE_DIR}/rocksdb/version.h" ROCKSDB_VER_${ver}_LINE
       REGEX "^#define[ \t]+ROCKSDB_${ver}[ \t]+[0-9]+$")
     string(REGEX REPLACE "^#define[ \t]+ROCKSDB_${ver}[ \t]+([0-9]+)$"
-      "\\1" ROCKSDB_VERSION_${ver} "${ROCKDB_VER_${ver}_LINE}")
-    unset(${ROCKDB_VER_${ver}_LINE})
+      "\\1" ROCKSDB_VERSION_${ver} "${ROCKSDB_VER_${ver}_LINE}")
+    unset(${ROCKSDB_VER_${ver}_LINE})
   endforeach()
   set(ROCKSDB_VERSION_STRING
     "${ROCKSDB_VERSION_MAJOR}.${ROCKSDB_VERSION_MINOR}.${ROCKSDB_VERSION_PATCH}")
f='/guix/log/po/guix'>log</a><a href='/guix/tree/po/guix?id=b5e03030b0fd21bba86f1b5496ceee8997dc9756'>tree</a><a href='/guix/commit/po/guix?id=b5e03030b0fd21bba86f1b5496ceee8997dc9756'>commit</a><a href='/guix/diff/po/guix?id=b5e03030b0fd21bba86f1b5496ceee8997dc9756'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/po/guix'>
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<div class='path'>path: <a href='/guix/log/?id=b5e03030b0fd21bba86f1b5496ceee8997dc9756'>root</a>/<a href='/guix/log/po?id=b5e03030b0fd21bba86f1b5496ceee8997dc9756'>po</a>/<a href='/guix/log/po/guix?id=b5e03030b0fd21bba86f1b5496ceee8997dc9756'>guix</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/po/guix?id=b5e03030b0fd21bba86f1b5496ceee8997dc9756&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-07-12 18:16:48 +0200'>2024-07-12</span></td><td><a href='/guix/commit/po/guix?id=ff82e0f7b48cd0d4dd906f5d52ba5d4940222086'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>Change-Id: I691cef365279ee5c50208a87ef5372a47152508e
</span></span></td><td>Florian Pelz</td></tr>
<tr><td><span title='2024-06-03 00:27:12 +0200'>2024-06-03</span></td><td><a href='/guix/commit/po/guix?id=834a4195241806784d4b321b95f06d85f458ce18'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.sv.po: New file.
* po/doc/local.mk: Add 'sv' cookbook.
* po/doc/po4a.cfg (po4a_langs): Add 'sv'.
* doc/local.mk: Add 'sv' cookbook.
* doc/htmlxref.cnf: Update URLs for cookbook.
* doc/build.scm (%cookbook-languages): Add 'sv'.
* doc/guix-cookbook.texi (Top): Mention 'sv' cookbook.

Change-Id: Ibfeb7254f583f1c8827e8c2756bbb02880bcba46
</span></span></td><td>Florian Pelz</td></tr>
<tr><td><span title='2024-05-01 02:42:54 +0200'>2024-05-01</span></td><td><a href='/guix/commit/po/guix?id=8bf41c80ef13ea57e834f4e23d649bd99a3e08fc'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/packages/sv.po: New file.
* po/packages/LINGUAS: Add it.

Change-Id: I2ad4dfcb935ba0a4e79c15b86cee6826c6580729
</span></span></td><td>Florian Pelz</td></tr>