Merge bitcoin/bitcoin#24754: build: specify cmake build dir for multiprocess depends build

7c218da build: specify cmake build dir for multiprocess depends build (fanquake)

Pull request description:

  When no build dir is specified, cmake will warn:
  ```bash
  Preprocessing libmultiprocess...
  Configuring libmultiprocess...
  CMake Warning:
    No source or binary directory provided.  Both will be assumed to be the
    same as the current working directory, but note that this warning will
    become a fatal error in future CMake releases.
  ```

  It's unclear if this will actually ever become an error, but it's also easy
  enough to just supply the directory, and save this maybe breaking in
  future.

ACKs for top commit:
  ryanofsky:
    Code review ACK 7c218da. I guess the purpose of the warning is to encourage people not to build in the source directory, but reasons for encouraging this don't really apply to the depends build system, so it is appropriate to disable the warning.
  hebasto:
    ACK 7c218da, tested on Ubuntu 22.04.

Tree-SHA512: 6904f2095fe62cead4abc644ec888c5d836e54a3c0b2a84c467029116e5d14eba35190570acaa23c6831aed9a4a65898134480cc46cdb141279ec0dc6f534d5f

Author: fanquake

depends/packages/libmultiprocess.mk

@@ -6,7 +6,7 @@ $(package)_sha256_hash=$(native_$(package)_sha256_hash)
 $(package)_dependencies=native_$(package) capnp
 
 define $(package)_config_cmds
-  $($(package)_cmake)
+  $($(package)_cmake) .
 endef
 
 define $(package)_build_cmds

depends/packages/native_libmultiprocess.mk

@@ -6,7 +6,7 @@ $(package)_sha256_hash=9f8b055c8bba755dc32fe799b67c20b91e7b13e67cadafbc54c0f1def
 $(package)_dependencies=native_capnp
 
 define $(package)_config_cmds
-  $($(package)_cmake)
+  $($(package)_cmake) .
 endef
 
 define $(package)_build_cmds