Merge bitcoin#30970: build: Add missing USDT header dependency to kernel

ccd10fd build: Add missing USDT header dependency to kernel (Cory Fields)

Pull request description:

  Noticed while testing a branch that replaces `boost::multi_index` with a custom replacement.

  Currently depends builds pick up usdt and boost from the same path, and because boost always exists, the usdt path is implicitly included. So without boost, USDT isn't found.

  An alternative to this would be to disable USDT for the kernel. I'd be open to either approach.

ACKs for top commit:
  hebasto:
    ACK ccd10fd, the diff looks correct.
  fanquake:
    ACK ccd10fd

Tree-SHA512: 2f91b8d5c8b169f7b72323d9163b5201f606ccdab95de7085847d2a672d10f940f69642c2528226a5efa4c589af24ca3bb9dd909eed0993e4cecd9689b4bed2f

src/kernel/CMakeLists.txt

@@ -84,6 +84,7 @@ target_link_libraries(bitcoinkernel
     bitcoin_crypto
     leveldb
     secp256k1
+    $<TARGET_NAME_IF_EXISTS:USDT::headers>
   PUBLIC
     Boost::headers
 )