evas-wayland-egl: Fix evas wayland_egl engine crash on mesa driver

Summary:
Evas wayland_egl engine crashes on startup when it is running with mesa.
Evas is trying to get EGL / GLES extension function addresses where evas_gl_symbols.
It is called before eglGetDisplay. Then mesa considers that current egl platform is
X11 if it has no EGL_PLATFORM env var. This behavior of mesa is bad. But we should
provide workaround until it is fixed. Thus EGL_PLATFORM env var should be defined to
wayland before calling eglGetProcAddress.
@fix

Test Plan: run elementary_test under wayland with wayland_egl engine.

Reviewers: raster, stefan_schmidt, devilhorns

Reviewed By: devilhorns

Subscribers: cedric

Differential Revision: https://phab.enlightenment.org/D1312

src/modules/evas/engines/wayland_egl/evas_engine.c

@@ -100,6 +100,14 @@ gl_symbols(void)
 
    if (done) return;
 
+   /* FIXME: Remove this line as soon as eglGetDisplay() autodetection
+    * gets fixed. Currently it is incorrectly detecting wl_display and
+    * returning _EGL_PLATFORM_X11 instead of _EGL_PLATFORM_WAYLAND.
+    *
+    * See ticket #1972 for more info.
+    */
+   setenv("EGL_PLATFORM", "wayland", 1);
+
 #define LINK2GENERIC(sym) \
    glsym_##sym = dlsym(RTLD_DEFAULT, #sym);