CMake: Allow both glslang 15 and 16

CMake/DolphinLibraryTools.cmake

@@ -54,7 +54,42 @@ function(dolphin_find_optional_system_library library bundled_path)
   dolphin_optional_system_library(use_system ${library})
   string(TOUPPER ${library} upperlib)
   if(use_system)
-    find_package(${library} ${ARGN})
+    # Try a list of versions
+    # Will be obsoleted if cmake ever fixes https://gitlab.kitware.com/cmake/cmake/-/issues/26477
+    if("DOLPHIN_TRY_VERSIONS" IN_LIST ARGN)
+      list(FIND ARGN DOLPHIN_TRY_VERSIONS versions_idx)
+      list(REMOVE_AT ARGN ${versions_idx})
+      # Extract list of version-like elements from ARGN into version_list
+      set(version_list)
+      while(TRUE)
+        list(LENGTH ARGN len)
+        if(len EQUAL versions_idx)
+          break()
+        endif()
+        LIST(GET ARGN ${versions_idx} ver)
+        if(ver MATCHES "^[0-9]+(\\.[0-9]+)*$")
+          list(APPEND version_list "${ver}")
+          list(REMOVE_AT ARGN ${versions_idx})
+        else()
+          break()
+        endif()
+      endwhile()
+      # Quietly check all the listed versions
+      foreach(version IN LISTS version_list)
+        find_package(${library} ${version} ${ARGN} QUIET)
+        if(${library}_FOUND)
+          break()
+        endif()
+      endforeach()
+      # If none were found, find_package one version loudly so the user sees
+      if(NOT ${library}_FOUND)
+        list(GET version_list 0 first_version)
+        find_package(${library} ${first_version} ${ARGN})
+      endif()
+    else()
+      find_package(${library} ${ARGN})
+    endif()
+
     # Yay for cmake packages being inconsistent
     if(DEFINED ${library}_FOUND)
       set(prefix ${library})

CMakeLists.txt

@@ -646,7 +646,7 @@ dolphin_find_optional_system_library_pkgconfig(FMT
 add_subdirectory(Externals/imgui)
 add_subdirectory(Externals/implot)
 
-dolphin_find_optional_system_library(glslang Externals/glslang 15.0)
+dolphin_find_optional_system_library(glslang Externals/glslang DOLPHIN_TRY_VERSIONS 15 16)
 
 # SPIRV-Cross is used on Windows for GLSL to HLSL conversion for the Direct3D 11 and Direct3D 12
 # video backends, and on Apple devices for the Metal video backend.