From: Alberto Garcia <berto@igalia.com>
Description: Enable THREADS_PREFER_PTHREAD_FLAG
 This fixes a FTBFS in riscv64
Bug: https://bugs.webkit.org/show_bug.cgi?id=182622
Bug-Debian: https://bugs.debian.org/895969
Origin: https://trac.webkit.org/changeset/231843
--- a/Source/cmake/OptionsGTK.cmake
+++ b/Source/cmake/OptionsGTK.cmake
@@ -6,6 +6,7 @@ WEBKIT_OPTION_BEGIN()
 SET_PROJECT_VERSION(2 50 4)
 
 set(USER_AGENT_BRANDING "" CACHE STRING "Branding to add to user agent string")
+set(THREADS_PREFER_PTHREAD_FLAG ON)
 
 # Update Source/WTF/wtf/Platform.h to match required GLib versions.
 find_package(GLIB 2.70.0 REQUIRED COMPONENTS gio gio-unix gobject gthread gmodule)
--- a/Source/cmake/OptionsJSCOnly.cmake
+++ b/Source/cmake/OptionsJSCOnly.cmake
@@ -1,3 +1,4 @@
+set(THREADS_PREFER_PTHREAD_FLAG ON)
 find_package(Threads REQUIRED)
 
 if (MSVC)