Override CMAKE_AR/CMAKE_RANLIB, fixes flatpak builds, also use lld wi…

…th clang if found (melonDS-emu#828)

* Override CMAKE_AR/CMAKE_RANLIB, fixes flatpak builds, also use lld with clang if found

* Ensure we build with -fPIC/-pie for LTO builds

CMakeLists.txt

@@ -74,8 +74,20 @@ if (CMAKE_BUILD_TYPE STREQUAL Release)
 endif()
 
 if (ENABLE_LTO)
-    add_compile_options(-flto)
-	add_link_options(-flto -fuse-linker-plugin)
+	add_compile_options(-flto -fPIC)
+	add_link_options(-flto -fuse-linker-plugin -pie)
+endif()
+
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+	set(CMAKE_AR "gcc-ar")
+	set(CMAKE_RANLIB "gcc-ranlib")
+elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+	find_program(LLD NAMES ld.lld ld64.lld lld-link)
+	if (NOT LLD STREQUAL "LLD-NOTFOUND")
+		add_link_options(-fuse-ld=lld)
+	endif()
+	set(CMAKE_AR "llvm-ar")
+	set(CMAKE_RANLIB "llvm-ranlib")
 endif()
 
 option(BUILD_QT_SDL "Build Qt/SDL frontend" ON)