【Build】Don't set PLATFORM_LINUX for either Web or Android

CMakeLists.txt

@@ -78,19 +78,19 @@ endif()
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 
 # Linux -pthread shenanigans
-if (CMAKE_SYSTEM_NAME STREQUAL Linux)
+if ((CMAKE_SYSTEM_NAME STREQUAL Linux) AND NOT EMSCRIPTEN AND NOT ANDROID)
     set(THREADS_PREFER_PTHREAD_FLAG ON)
     find_package(Threads REQUIRED)
     find_package(ALSA REQUIRED)
     set(PLATFORM_LINUX TRUE)
 endif()
-if (UNIX AND NOT APPLE AND NOT PLATFORM_LINUX)
+if (UNIX AND NOT APPLE AND NOT PLATFORM_LINUX AND NOT EMSCRIPTEN)
   set(PLATFORM_FREEBSD TRUE)
   find_package(ALSA REQUIRED)
   link_directories(/usr/local/lib)
 endif()
 
-if (UNIX AND NOT APPLE AND NOT ANDROID)
+if (PLATFORM_LINUX OR PLATFORM_FREEBSD)
     find_package(X11 REQUIRED)
 endif()
 # TinyFileDialogs