ci: drop Bitcoin Core example-target reference during subtree replace

Bitcoin Core's cmake/libmultiprocess.cmake currently references the
mpcalculator, mpprinter and mpexample targets, which no longer exist
in the subtree (the example/ directory lives outside the 'lib' branch).

Strip the offending line as part of replace_subtree so the bitcoin-core
CI job configures cleanly. Remove this workaround once a matching
Bitcoin Core PR has landed.

Author: Sjors

ci/scripts/bitcoin_core_ci.sh

@@ -14,6 +14,12 @@ replace_subtree() {
   # branch, which is 'git subtree split --prefix=lib' of master. Replace the
   # subtree with the same lib/ contents the split branch would publish.
   cp -a _libmultiprocess/lib src/ipc/libmultiprocess
+  # The example/ directory is intentionally not part of the 'lib' branch, so
+  # the mpcalculator/mpprinter/mpexample targets do not exist. Drop the line
+  # in Bitcoin Core's cmake glue that references them. Remove this once
+  # Bitcoin Core no longer references the example targets.
+  sed -i '/set_target_properties(mpcalculator mpprinter mpexample/d' \
+    cmake/libmultiprocess.cmake
 }
 
 add_llvm_apt_repository() {