CMakeLists: Add a namespace to the export

Avoids potentially dumping boost, fmt, and xbyak targets into a
top-level namespace without any qualification, which can lead to build
errors in projects that already make use of them.

src/CMakeLists.txt

@@ -294,4 +294,8 @@ if (CMAKE_SYSTEM_NAME STREQUAL "Windows")
     target_compile_definitions(dynarmic PRIVATE FMT_USE_WINDOWS_H=0)
 endif()
 
-export(TARGETS dynarmic boost fmt xbyak FILE "dynarmic-config.cmake")
+export(
+    TARGETS   dynarmic boost fmt xbyak
+    NAMESPACE dynarmic::
+    FILE      "dynarmic-config.cmake"
+)