build: various cmake fixes (#21902)

* build: various cmake refactors and simplifications

- Add STATUS keyword to message to ensure messages are shown in the
  correct order.
- Remove DEPS_CXX_COMPILER as we don't rely on C++ for any of our
  dependencies.
- Simplify how msgpack and luv configure options are constructed.
- Rely on the default installation for luv instead of manually passing
  configure, build and install commands.
- Simplify return code conditional.

* build: remove CMAKE_OSX_ARCHITECTURES_ALT_SEP workaround

CMAKE_OSX_ARCHITECTURES_ALT_SEP was defined as a workaround to prevent
the shell from interpreting `;`, which CMake uses as a list separator.
However, the same thing can be achieved by instead passing
CMAKE_OSX_ARCHITECTURES as a cache variable instead, which is a more
idiomatic way of achieving the same thing.

* build: define CMAKE_BUILD_TYPE before adding it to BUILD_TYPE_STRING

The problem with the current setup is that CMAKE_BUILD_TYPE is defined
after BUILD_TYPE_STRING. BUILD_TYPE_STRING will then be empty on the
first run, meaning that dependencies are built without a build type.
However, since CMAKE_BUILD_TYPE is a cache variable its value will
persist in subsequent runs. On the second run BUILD_TYPE_STRING will
have the correct value, but it's a different value from the ones the
dependencies were built with. This will force some dependencies to be
built again.

Fixes https://github.com/neovim/neovim/issues/21672.

cmake.deps/CMakeLists.txt

@@ -12,13 +12,13 @@ list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake" "${PROJECT_SOURCE_DI
 include(CheckCCompilerFlag)
 include(Util)
 
+set_default_buildtype()
+
 get_property(isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
 if(NOT isMultiConfig)
   set(BUILD_TYPE_STRING -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE})
 endif()
 
-set_default_buildtype()
-
 set(DEFAULT_MAKE_CFLAGS CFLAGS+=-g)
 
 check_c_compiler_flag(-Og HAS_OG_FLAG)
@@ -107,27 +107,16 @@ endif()
 
 set(DEPS_C_COMPILER "${CMAKE_C_COMPILER}")
 
-if(CMAKE_CXX_COMPILER)
-  set(DEPS_CXX_COMPILER "${CMAKE_CXX_COMPILER}")
-endif()
-
 if(CMAKE_OSX_SYSROOT)
   set(DEPS_C_COMPILER "${DEPS_C_COMPILER} -isysroot${CMAKE_OSX_SYSROOT}")
-  if(DEPS_CXX_COMPILER)
-    set(DEPS_CXX_COMPILER "${DEPS_CXX_COMPILER} -isysroot${CMAKE_OSX_SYSROOT}")
-  endif()
 endif()
 
 if(CMAKE_OSX_ARCHITECTURES)
-  string(REPLACE ";" "|" CMAKE_OSX_ARCHITECTURES_ALT_SEP "${CMAKE_OSX_ARCHITECTURES}")
   # The LuaJIT build does not like being passed multiple `-arch` flags
   # so we handle a universal build the old-fashioned way.
   set(LUAJIT_C_COMPILER "${DEPS_C_COMPILER}")
   foreach(ARCH IN LISTS CMAKE_OSX_ARCHITECTURES)
     set(DEPS_C_COMPILER "${DEPS_C_COMPILER} -arch ${ARCH}")
-    if(DEPS_CXX_COMPILER)
-      set(DEPS_CXX_COMPILER "${DEPS_CXX_COMPILER} -arch ${ARCH}")
-    endif()
   endforeach()
 endif()
 
@@ -140,7 +129,7 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
                     OUTPUT_STRIP_TRAILING_WHITESPACE)
     set(CMAKE_OSX_DEPLOYMENT_TARGET "${MACOS_VERSION}")
   endif()
-  message("-- Using deployment target ${CMAKE_OSX_DEPLOYMENT_TARGET}")
+  message(STATUS "Using deployment target ${CMAKE_OSX_DEPLOYMENT_TARGET}")
 endif()
 
 include(ExternalProject)