Update CMakeLists.txt to support Emscripten

CMakeLists.txt

@@ -421,6 +421,24 @@ if (FMT_TEST)
   add_subdirectory(test)
 endif ()
 
+if(EMSCRIPTEN)
+    set(FMT_WASM_SOURCES
+        ${FMT_SOURCES}
+        ${FMT_HEADERS}
+    )
+    add_executable(fmt_wasm
+        ${FMT_WASM_SOURCES}
+    )
+    target_include_directories(fmt_wasm PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/include
+    )
+    set_target_properties(fmt_wasm PROPERTIES COMPILE_FLAGS "-Os -s SIDE_MODULE=1 ")
+    set_target_properties(fmt_wasm PROPERTIES LINK_FLAGS    "-Os -s WASM=1 -s SIDE_MODULE=1 -s STANDALONE_WASM --no-entry")
+    set(CMAKE_EXECUTABLE_SUFFIX ".wasm")
+
+endif()
+
+
 # Control fuzzing independent of the unit tests.
 if (FMT_FUZZ)
   add_subdirectory(test/fuzzing)