compositor-android: fix build flags
compositor-android: fix build flags

When adding a C++ file to the build, I forgot to set CXXFLAGS for it,
triggering the error:

android-framebuffer.h:26:21: fatal error: EGL/egl.h: No such file or
directory

I never hit this, because I have EGL headers installed also in my
system, rather than only in $prefix.

Fix this by setting the CXXFLAGS for the android backend.

Reported-by: Scott Moreau <9e5433b3e9d7a89bc392ca03f89ec485f417b863@gmail.com>
Reported-by: Tiago Vignatti <f080760b2054d506aacc8dee97f8804c19fbc3aa@intel.com>
Signed-off-by: Pekka Paalanen <6c0263d81461c956d504307112a4ce25eaacc3d1@gmail.com>

krezovic/weston,udoprog/weston,mchalupa/weston,jonnylamb/weston,xorgy/weston,udoprog/weston,Tarnyko/weston-xdg_surface_present,jonnylamb/weston,giucam/weston,giucam/weston,Tarnyko/weston-xdg_surface_present,krezovic/weston,mchalupa/weston,Fantu/compositor-spice,kwm81/weston,xorgy/weston,Fantu/compositor-spice,kwm81/weston,sir-murray/weston,Gnurou/weston,Fantu/compositor-spice,eyolfson/weston,eyolfson/weston,sir-murray/weston,Gnurou/weston