testshader: add -sLEGACY_GL_EMULATION for emscripten

test/CMakeLists.txt

@@ -406,6 +406,9 @@ add_sdl_test_executable(testscale NEEDS_RESOURCES TESTUTILS SOURCES testscale.c)
 add_sdl_test_executable(testsem NONINTERACTIVE NONINTERACTIVE_ARGS 10 NONINTERACTIVE_TIMEOUT 30 SOURCES testsem.c)
 add_sdl_test_executable(testsensor SOURCES testsensor.c)
 add_sdl_test_executable(testshader NEEDS_RESOURCES TESTUTILS SOURCES testshader.c)
+if(EMSCRIPTEN)
+    target_link_options(testshader PRIVATE "-sLEGACY_GL_EMULATION")
+endif()
 add_sdl_test_executable(testshape NEEDS_RESOURCES SOURCES testshape.c ${glass_bmp_header})
 add_sdl_test_executable(testsprite MAIN_CALLBACKS NEEDS_RESOURCES TESTUTILS SOURCES testsprite.c)
 add_sdl_test_executable(testspriteminimal SOURCES testspriteminimal.c ${icon_bmp_header})