build: simplify dependency graph

Allow the objects of static libs to be built in parallel rather than serially
based on their dependency ordering.

For more detail, see:
https://cmake.org/cmake/help/latest/prop_tgt/OPTIMIZE_DEPENDENCIES.html

CMakeLists.txt

@@ -71,6 +71,13 @@ set(CMAKE_CXX_EXTENSIONS OFF)
 
 list(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake/module)
 
+# Flatten static lib dependencies.
+# Without this, if libfoo.a depends on libbar.a, libfoo's objects can't begin
+# to be compiled until libbar.a has been created.
+if (NOT DEFINED CMAKE_OPTIMIZE_DEPENDENCIES)
+  set(CMAKE_OPTIMIZE_DEPENDENCIES TRUE)
+endif()
+
 #=============================
 # Configurable options
 #=============================

cmake/minisketch.cmake

@@ -74,6 +74,9 @@ add_library(minisketch STATIC EXCLUDE_FROM_ALL
   ${PROJECT_SOURCE_DIR}/src/minisketch/src/fields/generic_8bytes.cpp
 )
 
+# Workaround for https://gitlab.kitware.com/cmake/cmake/-/issues/24058
+set_target_properties(minisketch PROPERTIES OPTIMIZE_DEPENDENCIES OFF)
+
 target_include_directories(minisketch
   PUBLIC
     $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/src/minisketch/include>

src/util/CMakeLists.txt

@@ -36,6 +36,9 @@ add_library(bitcoin_util STATIC EXCLUDE_FROM_ALL
   ../sync.cpp
 )
 
+# Workaround for https://gitlab.kitware.com/cmake/cmake/-/issues/24058
+set_target_properties(bitcoin_util PROPERTIES OPTIMIZE_DEPENDENCIES OFF)
+
 target_link_libraries(bitcoin_util
   PRIVATE
     core_interface