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}")
b32e170'>refs</a><a class='active' href='/guix/log/gnu/installer/hardware.scm'>log</a><a href='/guix/tree/gnu/installer/hardware.scm?id=25e5d205e0f83adc43024d4dd2cf91245b32e170'>tree</a><a href='/guix/commit/gnu/installer/hardware.scm?id=25e5d205e0f83adc43024d4dd2cf91245b32e170'>commit</a><a href='/guix/diff/gnu/installer/hardware.scm?id=25e5d205e0f83adc43024d4dd2cf91245b32e170'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/installer/hardware.scm'>
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<div class='path'>path: <a href='/guix/log/?id=25e5d205e0f83adc43024d4dd2cf91245b32e170'>root</a>/<a href='/guix/log/gnu?id=25e5d205e0f83adc43024d4dd2cf91245b32e170'>gnu</a>/<a href='/guix/log/gnu/installer?id=25e5d205e0f83adc43024d4dd2cf91245b32e170'>installer</a>/<a href='/guix/log/gnu/installer/hardware.scm?id=25e5d205e0f83adc43024d4dd2cf91245b32e170'>hardware.scm</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/gnu/installer/hardware.scm?id=25e5d205e0f83adc43024d4dd2cf91245b32e170&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-11-15 12:16:43 +0100'>2022-11-15</span></td><td><a href='/guix/commit/gnu/installer/hardware.scm?id=514fedbf3966b7fbab31a6c63b4210ec8b5b0c9a'>installer: Report known-unsupported PCI devices.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/hardware.scm: New file.
* gnu/local.mk (INSTALLER_MODULES): Add it.
* po/guix/POTFILES.in: Add it.
* gnu/installer.scm (installer-steps): Pass #:pci-database to the
'welcome' step procedure.
* gnu/installer/newt.scm (welcome-page): Add #:pci-database and pass it
to 'run-welcome-page'.
* gnu/installer/newt/welcome.scm (check-hardware-support): Add #:pci-database.
Enumerate unsupported PCI devices and run an error page when unsupported
devices are found.
(run-welcome-page): Add #:pci-database and pass it to
'check-hardware-support' and to the recursive call.
* gnu/installer/record.scm (&lt;installer&gt;)[welcome-page]: Adjust comment.
* doc/guix.texi (Hardware Considerations): Mention it.
</span></span></td><td>Ludovic Courtès</td></tr>