Merge bitcoin#27496: depends: reuse _config_opts for CMake options

63c0c4f depends: reuse _config_opts for CMake options (Cory Fields)

Pull request description:

  Context: I'm [currently experimenting with building our depends with CMake when possible](https://github.com/theuni/bitcoin/commits/depends-cmake) as part of our future transition to CMake. Specifically zmq, libevent, libnatpmp, and miniupnpc all have existing CMake buildsystems. Building them with CMake will allow us to drop several deps that we currently have (autoconf, automake, pkg-config, etc) which would be unfortunate to carry over after the switch-over.

  But that's not relevant for this PR. This is just a very simple change that makes the above work easier to experiment with as it [adds a needed feature for CMake packages](theuni@5733dc2#diff-e6ed342a25092e0a6d0308e0bfd826044578847132cc6726ac4afa2ca767b61aR20). It's a no-op for the current builds.

  ---

  From commit description:

  This will allow us to use the existing machinery for filtering by arch, os, debug/release, etc.

  For example, the following becomes possible for libevent when building with CMake:

  `$(package)_config_opts_release=-DEVENT__DISABLE_DEBUG_MODE`

  Now the define is only set when not building depends with DEBUG=1

ACKs for top commit:
  hebasto:
    ACK 63c0c4f

Tree-SHA512: 17d123219d2f98c017880196966ffebd5d09d3e2db8e443e227eb7e49da46e9d971fbe7fd2b99a324fc367e1bbe0ac3cd15b399bce98dd87fbb144d767e15fe7

depends/funcs.mk

@@ -175,7 +175,7 @@ $(1)_cmake=env CC="$$($(1)_cc)" \
                CXX="$$($(1)_cxx)" \
                CXXFLAGS="$$($(1)_cppflags) $$($(1)_cxxflags)" \
                LDFLAGS="$$($(1)_ldflags)" \
-             cmake -DCMAKE_INSTALL_PREFIX:PATH="$$($($(1)_type)_prefix)" $$($(1)_cmake_opts)
+             cmake -DCMAKE_INSTALL_PREFIX:PATH="$$($($(1)_type)_prefix)" $$($(1)_config_opts)
 ifeq ($($(1)_type),build)
 $(1)_cmake += -DCMAKE_INSTALL_RPATH:PATH="$$($($(1)_type)_prefix)/lib"
 else

depends/packages/libmultiprocess.mk

@@ -10,8 +10,8 @@ endif
 
 define $(package)_set_vars :=
 ifneq ($(host),$(build))
-$(package)_cmake_opts := -DCAPNP_EXECUTABLE="$$(native_capnp_prefixbin)/capnp"
-$(package)_cmake_opts += -DCAPNPC_CXX_EXECUTABLE="$$(native_capnp_prefixbin)/capnpc-c++"
+$(package)_config_opts := -DCAPNP_EXECUTABLE="$$(native_capnp_prefixbin)/capnp"
+$(package)_config_opts += -DCAPNPC_CXX_EXECUTABLE="$$(native_capnp_prefixbin)/capnpc-c++"
 endif
 endef