depends: Switch libmultiprocess packages to use local git subtree

With newly introduced libmultiprocess subtree, there's no need for depends
system to download and track changes to the upstream repository.

Note that adding the libmultiprocess subtree does not allow dropping
libmultiprocess packages from the depends build, because libmultiprocess
includes a code generation tool called mpgen, and in cross-compiled builds,
bitcoin core's cmake build system doesn't have access to a native toolchain and
can't build mpgen itself, so the depends system (or the native environment if
not using depends) needs to supply it.

depends/funcs.mk

@@ -39,9 +39,33 @@ define fetch_file
       $(call fetch_file_inner,$(1),$(FALLBACK_DOWNLOAD_PATH),$(3),$(4),$(5))))
 endef
 
+# Shell script to create a source tarball in $(1)_source from local directory
+# $(1)_local_dir instead of downloading remote sources. Tarball is recreated if
+# any paths in the local directory have a newer mtime, and checksum of the
+# tarball is saved to $(1)_fetched and returned as output.
+define fetch_local_dir_sha256
+    if ! [ -f $($(1)_source) ] || [ -n "$$(find $($(1)_local_dir) -newer $($(1)_source) | head -n1)" ]; then \
+        mkdir -p $(dir $($(1)_source)) && \
+        $(build_TAR) -c -f $($(1)_source) -C $($(1)_local_dir) . && \
+        rm -f $($(1)_fetched); \
+    fi && \
+    if ! [ -f $($(1)_fetched) ] || [ -n "$$(find $($(1)_source) -newer $($(1)_fetched))" ]; then \
+        mkdir -p $(dir $($(1)_fetched)) && \
+        cd $($(1)_source_dir) && \
+        $(build_SHA256SUM) $($(1)_all_sources) > $($(1)_fetched); \
+    fi && \
+    cut -d" " -f1 $($(1)_fetched)
+endef
+
 define int_get_build_recipe_hash
 $(eval $(1)_patches_path?=$(PATCHES_PATH)/$(1))
 $(eval $(1)_all_file_checksums:=$(shell $(build_SHA256SUM) $(meta_depends) packages/$(1).mk $(addprefix $($(1)_patches_path)/,$($(1)_patches)) | cut -d" " -f1))
+# If $(1)_local_dir is set, create a tarball of the local directory contents to
+# use as the source of the package, and include a hash of the tarball in the
+# package id, so if directory contents change, the package and packages
+# depending on it will be rebuilt.
+$(if $($(1)_local_dir),$(eval $(1)_sha256_hash:=$(shell $(call fetch_local_dir_sha256,$(1)))))
+$(if $($(1)_local_dir),$(eval $(1)_all_file_checksums+=$($(1)_sha256_hash)))
 $(eval $(1)_recipe_hash:=$(shell echo -n "$($(1)_all_file_checksums)" | $(build_SHA256SUM) | cut -d" " -f1))
 endef
 
@@ -64,10 +88,19 @@ $(1)_cached:=$(BASE_CACHE)/$(host)/$(1)/$(1)-$($(1)_version)-$($(1)_build_id).ta
 $(1)_build_log:=$(BASEDIR)/$(1)-$($(1)_version)-$($(1)_build_id).log
 endef
 
+# Convert a string to a human-readable filename, replacing dot, slash, and space
+# characters that could cause problems with dashes and collapsing them.
+define int_friendly_file_name
+$(subst $(null) $(null),-,$(strip $(subst ., ,$(subst /, ,$(1)))))
+endef
+
 define int_get_build_properties
 $(1)_build_subdir?=.
 $(1)_download_file?=$($(1)_file_name)
 $(1)_source_dir:=$(SOURCES_PATH)
+# If $(1)_file_name is empty and $(1)_local_dir is nonempty, set file name to a
+# .tar file with a friendly filename named after the directory path.
+$(if $($(1)_file_name),,$(if $($(1)_local_dir),$(eval $(1)_file_name:=$(call int_friendly_file_name,$($(1)_local_dir)).tar)))
 $(1)_source:=$$($(1)_source_dir)/$($(1)_file_name)
 $(1)_download_dir:=$(base_download_dir)/$(1)-$($(1)_version)
 $(1)_prefixbin:=$($($(1)_type)_prefix)/bin/