SDL: cmake: testshader needs -sLEGACY_GL_EMULATION on Emscripten

SDL Commits
1 
From a71e558d85ddd2fe0d20ca18a1c1c54955485ca7 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Tue, 1 Nov 2022 13:09:52 +0100
Subject: [PATCH] cmake: testshader needs -sLEGACY_GL_EMULATION on Emscripten

---
 test/CMakeLists.txt | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index f358b039b35f..c608f47b1f27 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -235,6 +235,9 @@ if(OPENGL_FOUND)
         target_link_libraries(testgl2 ${OPENGL_gl_LIBRARY})
     endif()
 endif()
+if(EMSCRIPTEN)
+    target_link_libraries(testshader -sLEGACY_GL_EMULATION)
+endif()
 
 file(GLOB RESOURCE_FILES *.bmp *.wav *.hex moose.dat utf8.txt)
 file(COPY ${RESOURCE_FILES} DESTINATION ${CMAKE_CURRENT_BINARY_DIR})