Revert MNX changes until it stabilizes

relevant discussion: #33865 (comment)

Author: kryksyh

CMakeLists.txt

@@ -173,6 +173,10 @@ option(MUSE_COMPILE_USE_UNITY "Use unity build" ON)
 option(MUSE_COMPILE_USE_COMPILER_CACHE "Try to use compiler cache: tries ccache, sccache, buildcache in that order. Use COMPILER_CACHE_PROGRAM to specify a specific compiler cache program." ON)
 option(MUSE_COMPILE_USE_SHARED_LIBS_IN_DEBUG "Build shared libs if possible in debug" OFF)
 
+# === System libraries ===
+# Important for the maintainers of Linux distributions
+option(MSS_USE_SYSTEM_MNXDOM "Try use system mnxdom" OFF)
+
 # === Debug ===
 option(MUE_ENABLE_ENGRAVING_RENDER_DEBUG "Enable rendering debug" OFF)
 option(MUE_ENABLE_ENGRAVING_LD_ACCESS "Enable diagnostic engraving check layout data access" OFF)

buildscripts/cmake/DependencyManifest.cmake

@@ -5,10 +5,3 @@ require_dep(opus)
 require_dep(libsndfile)
 
 require_source_dep(liblouis)
-
-if (MUE_BUILD_IMPEXP_MNX_MODULE)
-    require_dep(nlohmann_json)
-    require_dep(json_schema_validator)
-    require_source_dep(mnx_w3c)
-    require_source_dep(mnxdom)
-endif()

muse_deps

@@ -6,6 +6,26 @@
 
 muse_create_module(iex_mnx)
 
+include(FetchContent)
+
+set(mnxdom_BUILD_TESTING OFF CACHE BOOL "Do not build tests for mnx")
+if(MSS_USE_SYSTEM_MNXDOM)
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(mnxdom REQUIRED IMPORTED_TARGET mnxdom)
+    set(MNXDOM_LIB PkgConfig::mnxdom)
+    target_compile_definitions(iex_mnx PRIVATE MNXDOM_SYSTEM)
+    message(STATUS "Using system-installed mnxdom")
+else()
+    FetchContent_Declare(
+        mnxdom
+        GIT_REPOSITORY https://github.com/rpatters1/mnxdom.git
+        GIT_TAG        e7c947bf768caccf315426dcae0dfac02caf738b
+    )
+    FetchContent_MakeAvailable(mnxdom)
+    set(MNXDOM_LIB mnxdom)
+    message(STATUS "Using fetched mnxdom")
+endif()
+
 target_sources(iex_mnx PRIVATE
     mnxmodule.cpp
     mnxmodule.h
@@ -31,7 +51,7 @@ target_sources(iex_mnx PRIVATE
 )
 
 target_link_libraries(iex_mnx PRIVATE
-    mnxdom
+    ${MNXDOM_LIB}
     engraving
 )