Link EGL library when building with GLES support

When building for GLES platforms, SOIL2 uses eglGetProcAddress but the
EGL library wasn't being linked, causing undefined symbol errors at
runtime on systems like Raspberry Pi OS.

Fixes #926

Author: revmischa

vendor/SOIL2/CMakeLists.txt

@@ -52,6 +52,11 @@ if(NOT TARGET OpenGL::EGL)
             PRIVATE
             SOIL_NO_EGL
             )
+else()
+    target_link_libraries(SOIL2
+            PUBLIC
+            OpenGL::EGL
+            )
 endif()
 
 set_target_properties(SOIL2 PROPERTIES