Alert about Legacy SwiftShader debug build usage

SwiftShader's legacy OpenGL ES implementation should at this point no
longer be used for testing purposes. This change adds an assert that
eglCreateContext() no longer gets called.

Bug: b/147516027
Change-Id: I9dff50c039f598b099838dbf64e5327656c46ec5
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/64428
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Commit-Queue: Nicolas Capens <nicolascapens@google.com>
diff --git a/src/OpenGL/libEGL/libEGL.cpp b/src/OpenGL/libEGL/libEGL.cpp
index 85aa2ae..42f6c2be 100644
--- a/src/OpenGL/libEGL/libEGL.cpp
+++ b/src/OpenGL/libEGL/libEGL.cpp
@@ -818,6 +818,8 @@
 
 EGLContext EGLAPIENTRY CreateContext(EGLDisplay dpy, EGLConfig config, EGLContext share_context, const EGLint *attrib_list)
 {
+	ASSERT(false && "Legacy SwiftShader OpenGL ES is deprecated. Use SwANGLE instead.");
+
 	TRACE("(EGLDisplay dpy = %p, EGLConfig config = %p, EGLContext share_context = %p, "
 	      "const EGLint *attrib_list = %p)", dpy, config, share_context, attrib_list);